From time immemorial, the study of human behavior has been considered a territory in which molecular scientists, geneticists and other adherents of a “mechanistic” view of life have absolutely nothing to do: it is all so complex, spiritual and generally far from the banal interaction of molecules. However, gradually such a taboo is becoming a thing of the past, and many studies are already beginning to snatch from the darkness of the unknown individual details connecting genetics and behavior. This note is based on a short review published in the magazine Science, will successfully complement the material “ Genes control behavior, and behavior controls genes.", which appeared on the Elements website and is based on articles and reviews published in the same issue Science.

It is difficult to believe that human behavior and other aspects of higher nervous activity can be somehow related to genes. You can often hear, in response to a statement about, for example, gender (and therefore genetically predetermined) differences in mathematical abilities, an irritated statement like “Well then, show me the math gene!”. Of course, there is no “mathematics gene”, but this does not mean that mathematical abilities (as well as the more general abilities to concentrate attention, perceive abstract logical structures, etc.) are not “encoded” at the DNA level. The fact is that all complex phenomena, one way or another connected with higher nervous activity and not directly caused by some severe hereditary disease, are based on the most complex effects of the interaction of many genes, only creating opportunity formation of certain neural structures and personal characteristics, but certainly not determining them 100%. Even if a person had at least a thousand copies of the “mathematical gene” (if it existed), without the systematic development of abilities, of course, nothing would work out, and dreamers should remember this carefully. It’s just that many people probably have newspaper headlines like “The hard-hearted gene has been discovered” or “Divorce is genetically predetermined” can create the impression that both the successes and failures of people in all spheres of life can already be explained at the level of genes (but do readers of such newspapers know what are genes?), and, therefore, it’s not worth stressing too much.

Well, it would be convenient to explain poor social adaptation by heredity, and the behavior of all the “private traders” pruning and rushing from stripe to stripe by the gene of belligerence. Oh, by the way, were Hemingway’s famous depressions caused by problems with the dopamine receptor? Or maybe adultery is a direct consequence of the structural features of the vasopressin receptor gene? Research indicates a certain connection between these phenomena, although, of course, you should not explain your mistakes and other people’s successes solely by this.

Decades of research involving families and relatives, twins and adopted children have shown that there is a definite (and sometimes quite significant!) connection between genotype and a predisposition to a certain type of behavior in model situations, but that compared to the search for the most complex patterns that determine this connection, identifying mutations that cause development, for example, Huntington's disease, looks like child's play. It is now quite obvious that the ability to speak fluently and learn languages, responsiveness and willingness to help others and other spiritual qualities cannot be determined by any one gene, but are formed under the influence of many factors (of which the main one so far is probably still is education). In addition, the same gene is likely to be involved in many processes at once - for example, a predisposition to depression, overeating and impulsive behavior, making the task of establishing unambiguous connections almost impossible. The study of these factors is undoubtedly the most difficult task ever faced by geneticists, behaviorists and psychologists.

Love does not love...

Genetic scanning to determine the strength of marriage bonds? What? Doesn't it sound too much like the slogan of one of the magic salons? Despite the solid shade of yellowness of such a statement, one Canadian company actually offers for $99 to analyze the vasopressin 1a receptor gene in the applying couple ( AVPR1a), who gained scandalous fame as hard-hearted gene or divorce gene. However, how can such a test be more informative than the long-established chamomile fortune telling?

You can't explain everything by genes, but in Sweden they conducted a study involving 500 same-sex twins, each (or each) of whom had been in a state or civil marriage for at least five years. The subject of the study was the relationship between the structure of the promoter gene of the AVPR1a receptor gene and the results of a questionnaire, which included questions like “how often do you kiss your partner” or “how often do your interests and your partner’s interests intersect outside the family circle”. (This questionnaire was supposed to assess the “temperature” of family relationships.) It turned out that for men, the gene promoter sequence AVPR1a who were shorter (and several variants were found) were characterized by less strong attachment to their wives than the rest. These men are less likely to marry, and in marriage they are more likely to experience a crisis in family relationships. So, has the “divorce gene” been found? Perhaps there is no need to rush: the reality may turn out to be more complicated than this convenient scheme for revelers.

However, neither in family life nor in friendship are there such unambiguous connections as in pathophysiological conditions (although...), and, therefore, one should probably not rely on “genetic fortune tellers”.

I will survive

Some people are called weak-willed because they are unable to resist the circumstances around them and can be upset by even a minor incident, while others steadfastly overcome all adversities and inevitably move towards their goals. However, this kind of resilience seems to have something to do with genetics: emotional ups and downs are associated with a neurotransmitter serotonin, the transporter of which (SERT) will be discussed further.

In the now classic 1996 work by Klaus-Peter Lesch ( Klaus-Peter Lesch) it was found that the length of the regulatory sequences preceding the gene SERT, is also related to human behavior. In those of the 505 volunteers who were classified according to the questionnaire as susceptible to neuroses (depression, anxiety, etc.), a short regulatory sequence was identified, present in one or two copies, while in the more “calm” experimental subjects, a long variant of the promoter was found . The "short" form of the promoter causes more active secretion of serotonin into synapses, which has been shown in both animals and humans to cause anxiety and restlessness. However, one should not be deluded by the idea of ​​absolutely accurately predicting a person’s character based on the results of genotyping: according to statistical processing, the short form of the promoter SERT responsible for only 4% of depression and negative emotions. However, psychologists note that 4% in the case of personal qualities is already a lot, since before that scientists had not been able to discover a single gene in which variations provided at least this level of causality.

Another study, published in 2003, analyzed the relationship between stressful life events and related experiences in a group of 847 people who were surveyed for depression between the ages of 20 and 26. Among the subjects who did not have to experience “blows of fate” during this period (such as the death of loved ones, dismissal from work, personal failures, etc.), there was a significant connection between the gene SERT and the likelihood of depression was not identified (and this likelihood itself was low). The most interesting thing was in the group of people who experienced four or more stressful episodes: 43% were carriers of the “short” promoter isoform SERT reported a depressive period associated with troubles, while among the owners of the “long” version the number of depressions was almost two times lower. In addition, it was found that in people with a “short” promoter SERT Depression is more common in adulthood if they experienced childhood abuse; in the other part of the studied group, such a pattern was not observed.

But even here, of course, it is premature to say anything concrete. Many scientists with numbers in hand prove that for such weak effects the size of the samples used is clearly insufficient, and the influence of serotonin and its transporter on physiology is so wide - sleep disorders, cardiovascular activity, schizophrenia, autism, and the state of search acute sensations - that one can only judge their influence on behavior in the most general terms.

The belligerence gene

In 2006, it was discovered that a special form of the gene may be responsible for the “famous” warlike behavior of the New Zealand Maori tribe. monoamine oxidase-A, responsible for the breakdown of neurotransmitters in the brain. (I wonder if the acronym MAO-A coincidentally resembles the word Maori?). According to New Zealand researcher Rod Lee ( Rod Lea), 60% of Asians (including Maoris) are carriers of a special, “militant” gene variant MAO-A, while among Caucasians this figure does not exceed 40%. However, Lee himself admits that blaming all social problems - such as aggressiveness, gambling and various addictions - on a single gene would be an oversimplification.

In another study, using magnetic resonance imaging of the brain, it was demonstrated that carriers of the “militant” allele MAO-A A special part of the brain, the amygdala, is significantly more excited ( amygdala) - in response to the presentation of emotional stimuli, such as images of scary or disgusting faces. (The amygdala, or amygdala, is a part of the brain that processes socially relevant information associated with emotions such as fear and mistrust.) The activity found appears to indicate that such people have a harder time controlling their emotions and are more likely to respond with aggression to any emotional stimuli.

In the case of a gene MAO-A, as well as for the serotonin transporter, it has been shown that those with the “belligerent” allele are more likely to have “conduct problems” if they were abused in childhood (and if not, then the likelihood of “antisociality” is almost threefold). times lower). How events in the sphere of human relationships - even such unpleasant ones as child abuse - are able to influence gene expression seems to remain a mystery.

Testosterone acts similarly as a “fly in the ointment” in the case of “antisocial” behavior: when comparing 45 male alcoholics, and even those with a criminal record, with a control group “without aggravating”, it turned out that the “brawlers” not only had a reduced expression of MAO-A (i.e., a “militant” allele is present), but the content is also increased testosterone. And although the “militant gene” is unlikely to be responsible for the entire range of social problems, it definitely has some influence on behavior (especially in a “cocktail” with testosterone).

Live fast, die young

What do Janis Joplin, Jimi Hendrix and Kurt Cobain have in common besides the fact that they are all members of the mystically famous 27 Club? The world of rock musicians is perhaps a good place to look for people with a disrupted (and sometimes completely crippled) system of positive reinforcements that forms the traditional scale of human values. In the case of such a violation, a person stops receiving positive emotions from everyday things that are pleasant to most people, and goes all out in search of unhealthy forms of new sensations such as addiction to alcohol, tobacco, drugs or gambling. However, is the dopamine receptor that responds to the neurotransmitter to blame? dopamine, the lack of which leads to a violation of the system of positive reinforcements?

The A1 allelic form of the dopamine D2 receptor does not “feel” dopamine very well, which possibly leads to a “dulling” of the sensations accompanying everyday actions. Some scientists believe that it is the D2 receptor polymorphism that causes addictions and a pronounced constant search for thrills, as well as antisocial behavior, including problems in relationships with other people.

A study involving 195 students at a New York state university showed that carriers of the A1 allele begin sexual activity earlier, but at the same time are less able to form long-term relationships. Another study showed that boys who are carriers of one A1 allele have a greater tendency to marginal and criminal behavior than those who have two A2 alleles. True, heterozygous A1/A2 “experimental subjects” demonstrated an even greater tendency of this kind, somewhat confusing the situation. One scientist even said about this gene that “there is still more smoke than fire here.”

By the way, in the last issue Science there has even been work that draws connections between gene variants DRD2 and commitment to a particular political party, arguing that people with two “highly effective” A2 alleles turn out to be more trusting and easier to join any parties.

It is clear that practically nothing is still understood in the genetics of behavior. However, something else is also clear - that psychologists will soon, in addition to outdated Eysenck tests and other questionnaires, have to arm themselves with modern tools for analyzing the genetic characteristics of the participants in their studies.

Prepared from Science news with abbreviations.

Literature

1. Proteins that "clump" in Huntington's disease have been identified;
2. Z. R. Donaldson, L. J. Young. (2008). Oxytocin, Vasopressin, and the Neurogenetics of Sociality. Science. 322 , 900-904;
3. Elements:“Genes control behavior, and behavior controls genes”;
4. H. Walum, L. Westberg, S. Henningsson, J. M. Neiderhiser, D. Reiss, et. al.. (2008). Genetic variation in the vasopressin receptor 1a gene (AVPR1A) associates with pair-bonding behavior in humans. Proceedings of the National Academy of Sciences. 105 , 14153-14156;
5. A. Knafo, S. Israel, A. Darvasi, R. Bachner-Melman, F. Uzefovsky, et. al.. (2008). Individual differences in allocation of funds in the dictator game associated with length of the arginine vasopressin 1a receptor RS3 promoter region and correlation between RS3 length and hippocampal mRNA. Genes Brain Behav. 7 , 266-275;
6. K.-P. Lesch, D. Bengel, A. Heils, S. Z. Sabol, B. D. Greenberg, et. al.. (1996). Association of Anxiety-Related Traits with a Polymorphism in the Serotonin Transporter Gene Regulatory Region. Science. 274 , 1527-1531;
7. A. Caspi. (2002). Role of Genotype in the Cycle of Violence in Maltreated Children. Science. 297 , 851-854;
8. J. H. Fowler, D. Schreiber. (2008). Biology, Politics, and the Emerging Science of Human Nature. Science. 322 , 912-914;
9. C. Holden. (2008). Parsing the Genetics of Behavior. Science. 322 , 892-895.

1.2. History of the development of behavioral genetics as a science.

1.3. The concept of a trait in behavioral genetics

1.4. Methods for assessing behavioral traits (behavioral phenotyping).

1.5. Some nprinciples of genetic analysis of behavior.

Chapter 2. Ways to implement genetic information at the level of behavior

2.1. Genetics of morphological features of the nervous system and their connection with variability of behavioral traits.

2.2. Relationship between behavior and some biochemical parameters.

2.3. Hormonal regulation of variability in behavioral traits and endocrinological genetics.

PART P. SPECIAL GENETICS OF BEHAVIOR OF REPRESENTATIVES OF SOME TAXONOMIC GROUPS.

Chapter 3. Genetics of bacterial behavior.

3.1. Genetic basis of social behavior of bacteria.

3.2. Genetics of chemotaxis in bacteria.

3.3. Self-identification and mutual recognition of bacteria.

Chapter 4. Genetics of behavior of single-celled animals

4.1. Peculiarities of behavior of unicellular animals.

4.2. Genetics of ciliate behavior

4.3. Behavioral genetics of Dictyostelium discoideum

Chapter 5. Genetics of behavior of invertebrate animals.

5. 1. Genetics of roundworm behavior.

5. 2. Genetics of behavior of mollusks.

5. 3. Genetics of insect behavior

5.3.1. Insects as objects of behavioral genetics.

5.3.2. The influence of individual genes on insect behavior

5.3.3. Some aspects of the genetics of behavior of social insects.

5.3.4. Genetic basis of neurohumoral regulation of insect behavior.

5.3.5. Evolutionary aspects of insect behavior.

5.3.6. Genetics of sexual behavior of closely related locust species (Acridoidea)

Chapter 6. Genetics of Drosophila behavior.

6.1. History of the study of behavioral mutations in Drosophila.

6.2. Visual mutations in Drosophila.

6.3. Mutations of the motor system in Drosophila.

6.4. Temperature-sensitive mutations in Drosophila

6.5. Mutations that disrupt circadian rhythms in Drosophila

6.6. Mutations that change the sexual behavior of Drosophila.

6.7. Using mosaics to identify structures affected by behavioral mutations.

6.8. Method for localizing the focus of mutation action on the map of presumptive organs of Drosophila.

6.9. Selection-genetic method in the analysis of Drosophila behavior.

Chapter 7. Genetics of bird behavior.

7.1. Birds as an object of genetic analysis of behavior.

7.2. Environmental modification of some forms of innate behavior in birds.

7.3. Imprinting and its role in postnatal ontogenesis of brood birds.

7.4. Hybridological analysis of bird behavior.

7.5. Individual genes and behavioral traits of birds.

7.6. Evolutionary modification of bird behavior.

Chapter 8. Genetics of mammalian behavior.

8.1. Genetics of dog behavior.

8.2. Genetics of rodent behavior.

8.3. Genetics of cat behavior.

8.4. Genetics of behavior of horses and cattle.

8.5. Genetics of fox behavior.

Section 1. GENERAL ISSUES IN BEHAVIOR GENETICS.

Chapter 1. Introduction to the genetics of animal behavior.

1.1. Subject, goals, objectives, methods and place of behavioral genetics in the system of biological sciences.

Behavior - one of the most important ways of active adaptation of animals to a variety of environmental conditions. It ensures the survival and successful reproduction of both the individual and the species as a whole.

Behavior call the activity of a living organism aimed at interacting with the environment. Behavior is usually understood as outwardly manifested behavior, that is, those actions that can be noticed by an observer. In the most general understanding, behavior is a response formed by the body to signals received by it from the environment.

The behavior of animals at the organismal and supraorganismal levels became an independent subject of scientific research at the end of the 19th century. The term "animal behavior" was introduced as a scientific term in 1898 by zoologists C. Whitman and C.L. Morgan.

The study of animal behavior began simultaneously within three disciplines: zoology, psychology and physiology. Zoologists focused mainly on the study of species-specific behavior of animals, psychologists were interested in the behavior of animals in connection with the manifestation of certain mental abilities, and physiologists studied the neurophysiological mechanisms of behavior. Since the end of the 19th century, the entire field of study of animal behavior and psyche has been called zoopsychology.

By the middle of the twentieth century, two leading directions had emerged in the study of animal behavior: the American school of comparative psychology and the European school of ethology.

The direction of comparative psychology assumed that the behavior of animals is almost entirely formed by the external environment in the learning process, representing a combination of a few unconditioned and various conditioned reflexes. Representatives of the ethological school believed that animal behavior is genetically fixed and innate. They also argued that this behavior is based on complex mechanisms that are not limited to reflexes. Over time, both directions began to actively exchange ideas and mutually borrow research methods.

At the turn of the 70s. In the twentieth century, two more zoological directions appeared in the study of animal behavior - sociobiology and behavioral ecology. Interest has arisen in studying the development of behavior in ontogenesis.

Thus, animal behavior has long attracted the attention of biologists. Zoologists, ecologists, physiologists, and psychologists were interested in him. Behavior became the subject of study in ethology and animal psychology, and with the advent of the science of genetics, it also became the object of genetic analysis.

Behavioral genetics - a relatively young field of knowledge, formed at the intersection of genetics, developmental biology and a complex of sciences, which includes psychology, zoopsychology, ethology, environmental physiology and other disciplines. It is by its nature an interdisciplinary field of knowledge.

Thus, behavioral genetics is an integrated field of science, subject which is the study of the ontogenesis of a broad class of biological functions of the body called “behavior.”

In the process of its development, behavioral genetics turned out to be connected with such sciences as neurophysiology, endocrinology, psychiatry, biochemistry, anthropology, selection, evolutionary biology and many other sciences, uniting them around its problems.

Basic purpose behavioral genetics is to clarify the role of genetic factors in determining behavioral characteristics. Achieving this goal is related to the decision a number of tasks:

determination of the relative role and interaction of genetic and environmental influences in the formation of behavior in ontogenesis;

study of the heritability of stereotypical forms of adaptive behavior;

study of the mechanism of action of genes that determine the development of the nervous system;

studying the mechanisms of action of mutant genes affecting the function of the central nervous system;

study of genetic and population mechanisms of behavior formation and its changes in the process of microevolution.

An important problem in behavioral genetics has become the elucidation of the relative contribution of heredity and environmental influences in the formation of a behavioral phenotype. Geneticists agreed that any form of behavior is a genetically determined norm of reaction to the environment. But it was important for them to determine the relative contributions of genetic and environmental factors to the development of various forms of behavior.

It has been found that different behavioral effects occur in different environments, since genetic differences can not only be modified by environmental influences, but can be completely suppressed. Although the genotype of an animal remains constant throughout life, its behavioral characteristics can change significantly during ontogenesis. It is likely that the relative contribution of the genotype to individual differences may change during the development of the organism. It also changes in the process of evolutionary development. Being strictly genetically determined in simply organized animals, behavior, as organisms move through the stages of evolutionary development, gradually frees itself from the “dictation of individual genes”, acquires greater plasticity, dependence on the environment, ensuring the adaptive capabilities of the species in fluctuating and changing conditions. This does not mean that heredity loses control over behavior, but the forms of this control change significantly, providing evolutionary benefits for the species as a whole.

It should be noted that the term “environment” in behavioral genetics includes many factors that influence at all levels of organization of living things: molecular, cellular, tissue, organismal, supraorganismal levels.

The main areas of study of behavioral genetics include:

study of the determination of the ontogenesis of behavior and the genetic determination of behavioral reactions at the level of the whole organism;

studying correlations between some biochemical and behavioral phenotypes, identifying physiological and biochemical channels through which genetic information is realized at the level of behavior;

studying the role of behavior in microevolutionary processes and evolutionary modification of behavior itself;

study of the mechanisms of evolutionary genetic transformations of domestic animals, and also analysis of correlations between certain properties of behavior of domestic animals and productivity indicators;

study of genetic patterns that determine the polymorphism of hereditary diseases of the nervous system.

There are other directions as well. In modern genetics of behavior, the leading direction is called “neurogenetics”.

Neurogenetics is a discipline that has developed at the intersection of genetics, neuroscience and developmental biology. This is a branch of behavioral genetics, the subject of which is the study of hereditary mechanisms of activity of the nervous system.

Neurogenetics studies gene expression in connection with behavioral plasticity, deals with screening and positional cloning of mutations that affect behavior and brain function, carries out molecular genetic analysis of cognitive processes, studies morphogenetic, molecular and physiological mechanisms of development and functioning of the nervous system and features of the formation of nerve networks in ontogeny. To do this, scientists use molecular biological, biochemical, physiological and morphological methods.

Neurogeneticists study a wide variety of living objects. These include mammals, insects, mollusks, and amphibians. But preference is given to genetically well-studied objects, such as Drosophila (Fig. 1.a.) and mouse (Fig. 1.). Recently, rapidly reproducing objects have also been widely used - the worm Caenorhabditis (Fig. 2.) and the zebrafish (Fig. 3).

Fig.1.a. Drosophila melanogaster

Fig.1. Mouse Mus musculus

Fig.2. Nematode Caenorhabditis elegans

Fig.3. Zebrafish Danio rerio

Genetic studies of behavior and neurophysiological processes are carried out using two approaches:

the “gene to behavior” approach involves studying the function of a gene at the molecular and physiological levels with subsequent analysis of the influence of this gene on behavior;

The behavior-to-gene approach is aimed at studying the genetic component of behavioral variability, followed by analysis of individual chromosomes, gene complexes, and individual genes.

The “gene to behavior” approach is implemented by studying genes encoding enzymes and structural proteins that determine the general and specific characteristics of nerve cells and neuroglial cells. Genes encoding proteins associated with the function of the central nervous system as a whole are also studied. The influence of individual loci that determine the interaction of the brain with the endocrine system, as well as genes involved in the synthesis of chemical signaling substances and genes that determine the specific behavior of invertebrate animals, especially insects, is also being studied.

The approach “from behavior to genes” involves other experimental methods that differ from those used to analyze the work of individual genes. In such studies, it is important to select an adequate trait for analysis and adherence to the rules of genetic analysis of behavior. We need a sign that represents a natural “unit” of one or another form of behavior. The successful search for such a sign is associated with the neurophysiological basis of behavior.

The attention of researchers was attracted by different signs in different animal species: predisposition to seizures, general excitability, locomotor activity, orientation-exploratory reactions, various aspects of reproductive behavior, classical and instrumental conditioned reactions, reactivity to pharmacological substances.

To study the role of genotype in the formation of behavior, researchers more often chose either those traits that are easily quantifiable (for example, clear species-specific movements) or those traits that are easy to measure in terms of severity (for example, the level of locomotor activity, measured by the length of the animal's path traveled for a fixed period of experience).

Additional difficulties in conducting genetic research were caused by the fact that many behavioral traits depend very significantly on a number of factors external to the nervous system, for example, the season, the hormonal background of the body, etc. In addition, if clones are not taken into the experiment, then there is always a genetic component of variability in behavioral traits. Many of these traits can vary, revealing phenotypic variability within the normal reaction range, the range of which is determined by the genotype.

Behavioral traits are characterized by another specific form of variability - this is the variability of animal behavior traits, which is associated with the influence of individual experience, i.e. with different forms of learning, the formation of ideas, etc.

Behavioral genetics uses a variety of research methods: genetic, molecular biological, cytological, histological, biochemical, physiological, morphological and other methods of related sciences. The main group of methods, of course, are genetic.

Methods for studying the genetics of behavior improved as mathematical techniques for assessing quantitative traits were developed. It is the quantitative nature of many behavioral traits that allows them to be widely used in behavioral genetics. classical methods of quantitative genetics and selection. For example, analysis of phenotypic variation, its decomposition into paratypic and genotypic components; decomposition of the genotypic component into fixed (determined by additive interaction) and non-fixed (depending on dominance or epistatic interaction) components.

But the use of quantitative genetics methods in the analysis of behavior is fraught with significant difficulties, since many behavioral traits cannot be strictly quantified.

Classical hybridological analysis is used to a limited extent in behavioral genetics, but its modification is diallelic crosses - has found very wide application. This method allows you to analyze the results of a system of multiple crosses between several lines of animals. The essence of the method is to estimate the average values ​​of a trait and their variance in animals of several (at least three) inbred lines, as well as hybrids of all possible combinations. The result of using this method is to obtain the values ​​of variance components and values ​​characterizing the levels of covariation of traits in different genetic groups.

In addition to data on the nature of genetic variability of a behavioral trait, the results of diallelic crosses sometimes provide information essential for understanding the physiological processes underlying the manifestation of this trait.

To study the genetics of behavior of objects whose specific genetics are well studied, it becomes possible to carry out further stages of genetic analysis: decomposition of genetic variability into components depending on the contribution of individual linkage groups.

Behavior genetics uses and breeding methods . The first breeding experiments were devoted to studying the ability of rats to learn in a maze. Currently, selection of many behavioral traits is being carried out: motor activity, level of emotional reactivity, sexual behavior, alcohol preference, etc. The main results of selection experiments are the creation of lines of animals contrasting in their behavioral characteristics. The presence of such lines is of particular value in genetic studies of behavior, since, on the one hand, it allows for the targeted combination of genotypes fixed by selection, and on the other, it makes it possible to use cross-rearing and evaluate postnatal maternal effects.

But when selecting for complex behavioral traits, in the implementation of which various physiological systems (sensory, associative, effector) take part, the selection method turns out to be insufficient.

A widely used model in the genetics of animal behavior is creation of inbred lines. Inbred lines are populations of almost genetically identical individuals obtained by crossing full brothers and sisters over a series of generations. Recently, researchers have learned to obtain inbred lines through cloning.

Geneticists study genetically identical lines under different conditions. Since all individuals of an inbred line are considered genetically the same, observed differences in behavior may be due to pre- or postnatal environmental factors.

But the information that can be obtained from a simple comparison of inbred lines that differ in behavioral characteristics is quite contradictory. Therefore, scientists are busy looking for correlations of behavioral traits with neurophysiological and biochemical traits.

The current stage of development of science has enriched the genetics of behavior with such methods as recombinant inbred line method (RIL) and comparison of the nature of distributions of values ​​of various characteristics in the RIL group (strain distribution pattern), QTL method (quantitative trait loci) analysis, methods for creating and researching mosaic and chimeric animals, methods for creating transgenic organisms and knockout animals.

The method of recombinant inbred lines in some cases makes it possible to identify a small number of “main” genes that provide the greatest contribution to the variability of a given polygenic trait, as well as provide information about their localization in the chromosome.

The active development of molecular biological methods and the accumulation of data obtained with their help has made it possible to significantly improve the RIL method and successfully carry out mapping of quantitative trait loci (QTL analysis).

An effective molecular technology that has significantly increased the efficiency of the analysis of complexly inherited traits has become microarray analysis (microarray analysis), a method that allows you to study thousands of genes simultaneously. Using this method, the genome of an organism is extracted and placed in specific areas on a chip, which is previously kept in a solution containing RNA molecules expressed in certain types of cells and a fluorescent tag. If a given gene is expressed in a given cell type, RNA molecules from the solution bind complementarily to it (hybridize), which causes the corresponding segment to glow. The stronger the gene expression, the brighter the fluorescence.

Used in behavioral genetics and mutation models , since by operating with one gene, the researcher has more opportunities to elucidate the mechanisms by which this gene influences behavioral traits. In this case, several approaches are used. One of them is the study of the behavioral effects of already known mutations, for example those for which the biochemical mechanism of their manifestation has already been elucidated, for example, blocking the activity of certain enzymes. The second approach involves using existing or isolating new neurological mutations.

As interest in the evolutionary and population genetics of behavior increases, the tendency to use wild animals in experiments increases. Such studies examine differences in behavior resulting from biological specialization of closely related animal species or intraspecific divergence and use methods of evolutionary and population genetics.

Interesting results in the study of behavioral genetics have been shown by using knockout method (knockout study). This method is well developed for use in mice, but it is poorly developed for larger mammals and is not at all applicable to human studies. The knockout method involves inactivating a specific gene in stem cells. These cells are then placed into an embryo, which is implanted in the female's uterus. The gametes of the resulting offspring are checked for the presence of the disabled gene. And those that carry it are used in further selection to obtain a line of knockout mice, i.e. line, all animals in which have a deficiency of a specific gene. The behavior of these animals is compared with intact ones. If the behavior is different, it is concluded that the gene under study influences this behavioral response.

Using the knockout method, even small segments of DNA can be inserted or inactivated in order to determine the functions of the constituent parts of a gene. Researchers can also move a gene from one point in the genome to another to understand how the gene's location affects its expression.

Among the behavioral traits of mice studied using the knockout method are locomotor activity, exploratory behavior, learning and memory, social interactions and stress response.

To analyze human behavioral traits, classical methods of human genetics are actively and successfully used: family (genealogical) analysis, twin method, adopted children method, linkage analysis, association analysis.

Despite the variety of methods, historically there have been only a few approaches to the study of the genetics of behavior and the analysis of the inheritance of behavioral traits.

First approach consists of identifying behavioral differences between different lineages of the same species or between closely related species.

Second approach associated with the selection of animals for certain behavioral traits.

Third approach involves studying the influence of individual genes on behavior.

But with any of these approaches, behavioral geneticists face the same challenges.

The first difficulty is difficulty in unifying experimental conditions. Differences in the life experiences that animals have before the experiment influence their behavior during the experiment. Therefore, careful control of almost all experimental conditions is necessary; this is an absolutely necessary condition in studies on behavioral genetics.

The second difficulty relates to the difficulty of objective measurements. The element of subjectivity, which can be minimized in the analysis of biochemical, physiological and morphological traits, has a major impact on behavioral genetics research.

Finally, behavioral geneticists are faced with phenomena of learning and rational activity , and other areas of genetics usually do not deal with this. This circumstance can be considered the most significant unique feature of behavioral genetics as a specific branch of genetics.

It is difficult to study the genetic basis of behavior, primarily because behavioral traits are characterized by a wide reaction rate and high ontogenetic lability. Therefore, the genetics of behavior has not yet acquired the harmony and logical structure that is characteristic of other areas of genetics. But it closely interacts with them, uniting many related sciences around its topics. This integration function determines the place of behavioral genetics among other genetic sciences.

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COURSE WORK

“BEHAVIOR GENETICS: HOW MUCH AND HOW GENES CONTROL PERSONAL BEHAVIOR”

Introduction

Demographic, medical and technological changes associated with changes in society are occurring today so quickly that populations do not have time to adapt. Therefore, we need to better understand human behavior and its genetic basis.

Also, when teaching and raising children, it is important to know and take into account which abilities of the child are genetically determined, and which abilities are more amenable to external influence.

And when adopting children, parents need information about the genetic nature of a person in order to know which personality traits the child will retain from the biological parents and which can be changed.

In addition, behavioral genetics is important for the treatment and prevention of certain diseases, such as alcoholism, drug addiction and tobacco smoking, which are a huge problem today.

Based on what was written above, we can talk about the high degree of relevance of the issue we are studying.

Target: study how much and how genes can control behavior.

To achieve this goal, a consistent solution is proposed within the course work of the following tasks:

1) study the genetics of animal behavior;

2) study the latest discoveries about the possible genetic control of such human traits as temperament and level of intelligence;

3) study the genetics of human addictions.

Brief history of the issue

About genetics

Genetics is the science of heredity and variability of organisms. Genetics is a discipline that studies the mechanisms and patterns of heredity and variability of organisms, and methods for controlling these processes. It is intended to reveal the laws of reproduction of living things through generations, the emergence of new properties in organisms, the laws of individual development of an individual and the material basis of historical transformations of organisms in the process of evolution. The first two problems are solved by gene theory and mutation theory. Clarification of the essence of reproduction for a specific variety of life forms requires the study of heredity in representatives at different stages of evolutionary development. The objects of genetics are viruses, bacteria, fungi, plants, animals and humans. Against the background of species and other specificities, general laws are revealed in the phenomena of heredity for all living beings. Their existence shows the unity of the organic world. (eleven).

The history of genetics begins in 1900, when independently of each other Correns, Herman and de Vries discovered and formulated the laws of inheritance of traits, when G. Mendel’s work “Experiments on Plant Hybrids” was republished. Since that time, genetics has gone through three well-defined stages in its development - the era of Classical genetics (1900-1930), the era of neoclassicism (1930-1953) and the era of synthetic genetics, which began in 1953. At the first stage, the language of genetics was formed, research methods were developed, fundamental principles were substantiated, and basic laws were discovered. In the era of neoclassicism, it became possible to intervene in the mechanism of variability, the study of genes and chromosomes was further developed, the theory of artificial metagenesis was developed, which allowed genetics to move from a theoretical discipline to an applied one. A new stage in the development of genetics became possible thanks to the deciphering of the structure of the “golden” DNA molecule in 1953 by J. Watson and F. Crick. Genetics is moving to the molecular level of research. It has become possible to decipher the structure of the gene, determine the material basis and mechanisms of heredity and variability. Genetics has learned to influence these processes and direct them in the right direction. Wide possibilities for combining theory and practice have emerged. (17).

Behavioral genetics, a branch of behavioral science based on the laws of genetics and studying the extent and manner of differences in behavior are determined by hereditary factors. The main methods for studying genetic behavior in experimental animals are selection in combination with inbreeding (inbreeding), with the help of which the mechanisms of inheritance of forms of behavior are studied; in humans, statistical and genealogical analysis in combination with twin and cytogenetic methods. (5).

The dependence of behavior on hereditary factors - gene management and control of behavior - is studied at various levels of the organization of living things: in biocenoses, populations, communities, at the level of the organism, as well as at the physiological (organ, tissue, cell) and molecular levels. Research on the genetics of behavior has significant significance for the study of individual differences in higher nervous activity and identifying the relative role of congenital and individually acquired characteristics of behavior, for explaining the role of genetically determined characteristics of animal behavior in the population (for social animals - in a herd, flock, etc.), as well as for creating experimental models of nervous diseases. (3).

Behavioral genetics is a relatively young field of knowledge, which took shape about half a century ago at the intersection of such disciplines as genetics itself, developmental biology and a complex of behavioral sciences, including psychology, ethology and environmental physiology. The task of this new direction was to study the ontogenesis of a broad class of biological functions of the body, called “behavior” and providing essentially two-way communication between the individual and his surrounding ecological and social environment. The global nature of this task in itself was the reason that the sphere of interests of behavioral genetics soon became involved in such widely separated areas of science and practice as endocrinology and psychiatry, biochemistry and pedagogy, neurophysiology and linguistics, anthropology and breeding of farm animals. In addition, since it has long become obvious that behavior is one of the most important factors in the evolutionary process, the genetics of behavior in recent years has become more and more closely linked with evolutionary teaching, becoming an integral part of modern evolutionary biology. (16).

1. Genetic analysis of behavioranimals

Genetic research in humans has a number of understandable limitations. In this regard, studies of the genetic basis of behavior in animals are of interest. Here you can use selection methods, obtaining inbred lines, modern methods of genetic engineering, selectively turning off certain genes, causing mutations, etc. Inbred lines obtained through long-term inbreeding (at least 20 generations) represent animals identical in genotype, therefore all differences that can be observed among animals of the same line are associated with environmental influences. (10).

1.1 Genetics of insect behavior

genetics addiction animal control

Let us give an example of genetic analysis of behavior, which is quite often discussed in educational literature. We'll talk about bees and a disease called American larval rot. There is a line of bees that are resistant to this disease because if the disease occurs, the bee larvae will immediately unseal the cell they are in and remove it from the hive. This prevents the spread of the disease, and resistance to it is associated with characteristic behavior! When bees that are resistant to the disease are crossed with those that are not resistant, first generation hybrids (F1) are obtained that do not clean the hives. It is clear from this that the allele or alleles causing this type of behavior are recessive. The first generation F1 hybrids are again crossed with resistant bees (the so-called analytical crossing - with recessive homozygous individuals). As a result, the offspring exhibit four variant phenotypes in a 1:1:1:1 ratio. These are the options:

The bees open the cells and remove the affected larvae;

The cells are opened, but the affected larvae are not removed;

The cells are not opened, but the affected larvae are removed if the cell is opened by the experimenter;

Do not open the cells, do not remove the affected larvae.

Thus, it is obvious that this rather complex behavioral act is controlled by genes at only two loci. One allelic gene determines the actions of opening the cell, the other is associated with the removal of the affected larva.

In this case, it is impressive that quite complex actions can be controlled by just one gene.

In fruit flies - Drosophila, which for many years have been a favorite subject of geneticists - a huge number of mutations affecting behavior have been identified. Yes, mutation dunce leads to disruption of the ability to develop conditioned reflexes. There are several known mutations that somehow impair learning. It is important that all these defects are associated with impaired metabolism of so-called second messengers (primarily cyclic AMP), which play an important role in intracellular signaling and synaptic plasticity.

There are mutations that lead to high and low sexual activity, to the avoidance of certain odors, changing motor activity, even to the point that there is a mutation that determines how the Drosophila folds its wings - right over left or vice versa.

Sometimes there are examples of very specific behavioral deviations. So, with mutation fru (from fruitless- infertile), the following disturbances in sexual behavior are observed in males: they do not court females, but only court males homozygous for this mutation, and stimulate normal males to court themselves. The result was something like a model for the formation of homosexual behavior.

In general, one gets the impression that most behavioral acts in Drosophila are genetically predetermined in every detail. (8).

1.2 Animal learning studies

One of the most important properties of animal behavior is the ability to learn. Animal research provides an opportunity to conduct breeding experiments. Tryon was one of the first to conduct such an experiment on rats. He carried out selection based on the learning ability of animals, which had to find the correct path to feeding placed in a complex 17-dead-end maze. Animals that were good and poorly trained were selected and subsequently crossed only with each other. Regular selection gave a very quick result - starting from the eighth generation, the learning ability indicators of “smart” and “stupid” rats (the number of erroneous runs in the maze) did not overlap. Selection was carried out until the 22nd generation, as a result of which two groups of rats were obtained - well trained ( bright) and bad - ( dull). Under the same growing and testing conditions, differences between these groups are due only to differences in genotype.

Subsequently, many strains were obtained, especially in mice, differing in their ability to perform various forms of learning. Similar lines were selected for their ability to learn in the T-maze, for learning active and passive avoidance, and swimming in the Morris water test. Sometimes the task an animal performs is quite complex. For example, strains of mice were obtained that were good and bad at learning the food-procuring motor conditioned reflex. The mice were reinforced when they jumped in response to a sound or light stimulus onto different shelves. (9). In this case, some community patterns can be noted:

there is usually a large variation of the trait in the source population;

Although the selection response can manifest itself very early, and the difference between lines is detected after 2-3 generations, it takes much more generations (about 10-20) for stable, reliable differences between lines to appear.

The high spread of initial values ​​of the trait and the gradual development of the selection response are evidence of the polygenic nature of the trait. In other words, the manifestation of this trait in the phenotype depends on a relatively large number of genes. The same is true for most mammalian behavioral traits.

There is another problem associated with selection experiments. Selection is carried out when testing a specific task. Naturally, the question arises: to what extent does the ability to solve this problem correlate with the ability for other types of learning? There is no clear answer to this question.

For example, when they began to study in more detail the ability to learn in general on lines of rats obtained by Tryon ( bright And dull), it turned out that those who were well trained ( bright) learn food-procuring behavior faster, and rats dull in turn, demonstrate better performance in defensive reaction tasks. Thus, here the problem of learning can be transferred to the plane of motivational mechanisms. It is known that motivation can have an extremely strong impact on learning outcomes.

It turns out that the rat line bright are more motivated by hunger, while rats dull are more motivated by fear in threatening situations. Just like motivation, the success of learning can be influenced by sensory abilities, the level of motor activity, and the emotionality of animals. Accordingly, genes that influence the activity of these qualities can have an impact on learning.

However, some lineages also show differences in more general learning abilities. So, mouse lines DBA/2 J learn better than animal lines C.B.A., which is confirmed in a number of tests: during food reinforcement in the maze, in the shuttle chamber during the development of a conditioned reflex reaction of active avoidance, during operant learning. This means that there are certain genetically determined properties of the nervous system that affect the ability to implement various types of learning. The list of mutations that impair learning and memory in mice is rapidly expanding.

Table 1. Mouse genes localized on certain chromosomes and playing an important role in learning and memory

Chromosome	Learning and Memory
	Greb1

Differences in memory characteristics were also noted in Tryon's rats, which certainly affected the test results. So, it turned out that rats have lines bright consolidation occurs faster - strengthening of memory traces, their transition into a stable form. You can resort to influences that disrupt short-term memory, for example, using a special form of electric shock that causes amnesia. It turned out that already 75 s after training, electroshock amnesia cannot be induced in rats of the line bright, whereas on the rat line dull The electroshock procedure still has an effect.

Different speeds of consolidation appear to determine differences in the success of forming orientation skills in a maze. What happens if rats line dull will you be given enough time to memorize? Studies have shown that when the intervals between trials were 30 s, rats bright learned much faster than line rats dull, as it should have been. But when the interval was increased to 5 minutes, the difference in learning between the lines decreased significantly. If the rats were given only one trial per day, the learning performance of both strains became identical. The speed of skill acquisition and the speed of consolidation can be determined by different mechanisms!

An important conclusion: selection of learning conditions can reduce or even eliminate differences in genetically determined abilities.

Currently, a number of mouse strains have been obtained that differ sharply in the speed of memory consolidation. There is a line ( C3 H/ He), in which learning is possible only through continuous training. There is a line ( DBA/2 J), in which training, on the contrary, is much more successful when the intervals between individual training sessions increase. And finally, the line (BALB/c) was introduced, for which the nature of the intervals between experimental sessions does not affect the learning results. This approach thus creates unique opportunities for studying memory mechanisms.

Another area of ​​animal research is to elucidate the influence of the environment on the formation of behavioral properties. Let's go back to line rats again bright And dull. You can conduct an experiment to raise these rats in different conditions. One group (control) is grown under normal vivarium conditions. For the other, an “enriched” environment is created - large cells with painted walls, filled with various objects, mirrors, swords, ladders, stairs, tunnels. Finally, the third group is provided with an “impoverished” environment, where the influx of sensory stimuli is severely limited and the possibilities for search and exploratory activity are limited. In Table 2, the enriched environment is designated as “good” conditions, the depleted environment as “bad”. Normal conditions correspond to the control group.

Table 2. Results of training in a maze of lines of “smart” and “stupid” rats raised in deteriorated, normal and improved conditions. (15).

The results of the control group correspond to expectations - rats of the line bright when learning in a maze, they make much fewer mistakes compared to rats of the line dull. However, for rats raised in an enriched environment, this difference practically disappears, mainly due to a sharp decrease in errors in the “stupid” strain of rats. In the case of rearing in a depleted environment, the difference between the two lines also disappears, and this time mainly due to a sharp increase in the number of errors in the “smart” line of rats.

Here we touch upon a very important problem - the existence of powerful mechanisms of plasticity of the nervous system that are capable of compensating for very significant defects. Numerous studies on raising rats in an enriched environment have shown that relatively quickly - within 25-30 days, very significant morphological differences arise at the level of the cerebral cortex. Animals kept in an enriched environment have a thicker cortex, larger neuron sizes, and a 10-20% increase in the number of dendritic processes per neuron. All this leads to a 20% increase in the number of synapses per neuron. Ultimately, we are talking about billions of new synapses, which dramatically increases the capabilities of the nervous system. Particularly important is the fact that this plasticity potential is maintained almost all the time. Experiments on adult animals led to similar results.

Similarly, an enriched environment has an impact on a child’s development. (1).

2. Recent discoveries about the possible genetic control of such human traits as temperament andintelligence level

2.1 Genetics of temperament

In modern behavioral genetics, we are more often talking about personality characteristics, since the concept of temperament, especially in foreign literature, is currently associated mainly with the type of emotional reactions (especially their expression), as well as with the characteristic or habitual inclinations of the individual.

As a method for identifying the main personality traits, the approach of identifying five factors, the so-called “Big Five” ( Big Five).

Extroversion ( extraversion). Assessments are given for introversion - extraversion, sociability - unsociability, confidence - shyness.

Ability to agree ( agreeableness). Compliance is assessed - intransigence, friendliness - indifference to others, obedience - hostility.

Integrity ( conscientiousness). This is the most uncertain factor.

Neuroticism ( neuroticism). The level of emotional stability, adaptability - anxiety, dependence - independence is determined.

Frankness, directness ( openness). Ease of adaptability is determined - submission, disobedience - submission.

When analyzing the heritability of individual components of this list, the highest values ​​were obtained for extraversion (0.49) and frankness (0.45), and the lowest for agreeableness (0.35) and conscientiousness (0.38). For all indicators, the contribution of the general environment to variability remained close to zero (from 0.02 to 0.11). We can conclude that individual environmental effects or genotype-environment interactions play a major role in the variability of personal characteristics.

When studying symptoms of anxiety and fearfulness (a component of emotionality called neuroticism by other methods), it was found that approximately half of the observed variability could be attributed to genetic factors. These data were obtained from interviews with monozygotic twins, both reared together and separated. Studies that have included peer ratings of behavior in addition to self-report measures have found similar results.

Among the more specific personality traits, we should mention the degree of radicalism and conservatism in thinking. Contrary to expectations, it turned out that these qualities are characterized by rather high heritability estimates ( h 2 equal to 0.65 and 0.54, respectively). Even for such a trait as authoritarianism, the value was obtained h 2 = 0.62, and it was found that according to this characteristic there is an unexpectedly high value of assortative marriage (0.68!).

A large Minnesota study of twins reared apart conducted a wide variety of tests on personality and temperament, as well as on vocational interests, leisure activities, and social relationships. It turned out that monozygotic twins who grew up together showed approximately the same degree of similarity as twins who were separated. (4).

2.2 Intelligence

IQ ( IQ) is the most intensively studied psychological indicator in genetic research. Differences in human intelligence are obvious and can be very significant, but how accurately are they reflected in psychometric measures? The use of tests, sometimes excessively, leads to quite serious contradictions, since it is still unknown what is related to intelligence and what is not. The importance of such properties as the ability to learn and adapt is usually emphasized. Recently, the concept of metacognitive abilities has been added, which is understood as the ability to understand and control oneself.

It's important to remember that these studies are looking at "psychometric intelligence," which is the difference between people in test performance. These tests reflect different aspects of human behavior in different ways and do not cover all mental abilities. However, for a very wide range of these abilities, there is a test system that allows them to be more or less adequately assessed and has validity. (6).

General, or general, factor (g) cognitive abilities

The concept of general, or general, factor (g) of intelligence was introduced by Spearman (1904), who found a significant correlation in the success of solving a wide variety of tests assessing intellectual ability. The general intelligence factor thus reflects some basic quality necessary to perform all types of tasks. Over the subsequent time, the results of these experiments were reproduced many times, but many alternative opinions also appeared.

The nature of this common factor has always been a matter of debate. Some considered the g factor to be an epiphenomenon generated by the association of general cognitive tasks with linguistic skills and cultural knowledge. Other researchers explained the g factor by saying that tests depend on the involvement of general brain resources, represented either simply as brain structures or as certain cognitive modules. Jensen believes that the g factor reflects the speed and efficiency of neural processing of information. Finally, Plomin (1999) defends the position that this general factor reflects innate abilities associated with genetically determined inclinations. In other words, there is a certain set of genes that determines the properties of the general factor g. These interpretations are not mutually exclusive. So, it is obvious that both the points of view of Jensen and Plomin can be accepted if we imagine that genetically determined inclinations relate specifically to the speed and efficiency of the work of neural networks.

The question of how much the general g factor can be determined by genetic factors has been the subject of many studies conducted using all methods of genetics, including twins. All of them lead to the fact that genetic factors play a large role in determining g. Estimates of the heritability coefficient for the general factor g range from 40 to 80%; in general, it can be assumed that at least half of the observed variability in g is associated with genotypic variability. With age, the heritability coefficient increases (up to 60% in adults).

Another point of view on intelligence is intelligence toaka the sum of individual abilities

Some researchers generally argued that a general factor is not identified, but that there is a wide range of narrow abilities that do not correlate with each other. IQ is therefore a sum of individual abilities. There were up to 120 such specific abilities.

The modern concept of the hierarchy of intellectual abilities to some extent unites these conflicting points of view. On the one hand, there is undoubtedly the presence of a common factor (g), which thus constitutes a certain core of intellectual abilities (first level). This is experimentally confirmed by a significant correlation in the success of solving tests that allow assessing various mental abilities. It is believed that a common factor accounts for about 50% of the variability observed in a population in the ability to solve a wide range of different tests.

Part of the variability can be attributed to several smaller “group” factors of intelligence, of which the most frequently identified are memory, spatial abilities, information processing speed, and verbal (second level). Abilities that fall into different groups may show less correlation. As an example, we can cite the characteristics of intelligence in some cases of mental retardation associated with chromosomal mutations. In patients with Shereshevsky-Turner syndrome, verbal abilities are practically unimpaired (normal level of development), while spatial abilities are significantly reduced. A completely different picture is observed in the case of Klinefelter syndrome, in which a decrease in IQ is caused by serious impairments in verbal abilities, while spatial abilities remain normal.

Finally, some of the observed variability is not due to a general factor or to several group factors and is determined by very specific mental abilities (third level). Thus, we obtain a three-level model that well describes the existing correlations in the performance of various tests and the observed variability (dispersion) of abilities.

With age, IQ changes slightly, showing high stability over many decades. Individual abilities may change to varying degrees, some show some growth (vocabulary, general knowledge, certain skills), others gradually decline as they age, for example, the ability to abstract reasoning, memory, speed of information processing. This last factor is especially important because there is evidence showing that the observed changes in cognitive processes with aging are mainly associated with a decrease in the speed of information processing. (2).

HeritabilityIQ

In a study of monozygotic twins raised separately, a high degree of IQ correlation was found (ranging from 0.64-0.78). The heritability estimate (in the broad sense, i.e., taking into account all genetic factors) in these works was 0.75.

According to some other calculations, the heritability of this coefficient is estimated at 0.50, the contribution of the general environment is 0.20-0.30, and the rest of the phenotypic variance is accounted for by individual environmental influences and measurement error.

Direct assessment of the influence of the general environment is possible in studies of adopted children. If we calculate the correlation by IQ between natural and stepchildren raised in the same family, it is only 0.04 (data from four studies obtained on adults). Other evidence suggests that in early childhood there is little correlation between IQ genetically stepchildren raised in the same family. Moreover, with age, despite the increase in the duration of joint upbringing, the correlation drops to almost zero. These data indicate that there is no influence of the general family environment on the observed variability in mental ability.

Correlation IQ between children and their biological parents in all studies was significantly higher than between adopted children and adoptive parents (0.35-0.40 versus 0.15). Very interesting data were obtained in longitudinal studies. If a small correlation is recorded in early childhood IQ foster children and adoptive parents, then starting from the age of 7, the similarity between the level of intelligence of adopted children and their biological parents increases, and the “adopted children-adoptive parents” correlation decreases. With low IQ values ​​in biological parents, increased similarity between “adopted children and biological parents” is achieved by reducing IQ in children. Additionally, it was noted that this decline was not influenced by the socioeconomic status of the adoptive parents.

Most representative study IQ was based on Danish conscription data (1984). All men, regardless of fitness for service, took an intelligence test. The correlation of test results among siblings who grew up together was 0.52, for siblings who grew up in different families - 0.47, for stepbrothers and sisters who grew up separately, this figure did not exceed 0.22, and for adopted children who grew up in the same family - 0.02. Thus, the results indicate high heritability and little influence of shared environment.

Change in heritability coefficientincrease in intelligence with age

Longitudinal twin studies of intelligence have shown that at the age of 3-6 months there is virtually no difference in the correlation of mental abilities between mono- and dizygotic twins, i.e. heritability is zero. Then the difference manifests itself and gradually increases due to the fact that the similarity of monozygotic twins increases all the time, and the similarity of dizygotic twins decreases all the time. At age 15, the IQ correlation for monozygotic twins was 0.86 and for dizygotic twins was 0.54. In adults, correlation values IQ for monozygotic twins were 0.83, and for dizygotic twins - 0.39. During almost the entire adult period of life, heritability remained the same, not exceeding an average of 0.81.

The increase in heritability with age contradicts the assumption that environmental influences play an increasingly important role in the emergence of individual differences with age.

As we grow older and move from childhood to adulthood, there is a gradual decrease to almost zero in the contribution of the common (shared) environment to the observed variability IQ. The contribution of the individual environment remains relatively significant at all ages.

If we evaluate special mental abilities, then in general we obtain lower heritability values ​​than in the case of general mental abilities. IQ. From the mass of data on individual components of tests that determine mental abilities, it is worth mentioning an interesting fact regarding verbal abilities. The values ​​of the heritability coefficient for verbal abilities exceed those for non-verbal intelligence. This applies to a wide variety of studies, regardless of the specific heritability values, which can vary quite widely. It turns out that nonverbal abilities are more sensitive to environmental influences.

At the same time, twin studies revealed that memory for nonverbal stimuli is characterized by very high heritability. (13). For example, heritability coefficient values ​​were obtained for memory for non-verbal visual stimuli (0.93), tactile (0.69) and auditory (0.86). In contrast, for verbal stimuli, both visual and auditory, there were no significant differences in the performance of mono- and dizygotic twins. Thus, the values ​​of the heritability coefficient for memory for verbal stimuli turned out to be much lower (visual stimuli - 0.38; auditory stimuli - 0.37). (1).

3. Genetics of human addictions

3.1 Alcoholism

There is quite a wide variety of opinions regarding alcoholism. Some studies report high heritability rates, while others report the opposite. When analyzing, you should pay attention to the very definition of alcoholism. There may be a broad definition when all cases of excessive drinking are noted or when drinking is actively objected to by other family members. A broader definition is also possible, in which only cases with the occurrence of addiction and withdrawal symptoms are taken into account.

Another source of disagreement is the apparent difference between the sexes. Female and male alcoholism differ in both causes and manifestations.

At one time, it was discovered that there were no differences between mono- and dizygotic female twins in concordance for alcohol and drug abuse. Concordance values ​​were 0.34 and 0.31, respectively. In men, such differences turned out to be significant only for cases of early onset of alcohol abuse (before 20 years of age). It was concluded that only early forms of alcoholism in men are highly heritable. This is confirmed by the fact that in cases where both monozygotic male twins became alcoholics, a high incidence rate was simultaneously observed among their relatives. For women, such a pattern was not observed.

Other work, carried out on a larger number of female twin pairs, on the contrary, showed that concordance for a variety of manifestations of alcoholism for monozygotic pairs is twice as high as for dizygotic pairs. The heritability value for female alcoholism turned out to be at the level of 60% with a broad definition of alcoholism as drunkenness associated with the occurrence of life problems. At the same time, the impact of the common environment (common upbringing, attending the same school, having common neighbors, etc.) was practically zero. Thus, all environmental influences associated with the occurrence of alcoholism can be attributed to influences specific to a given individual. Interestingly, parental alcoholism not only did not increase the risk of alcoholism in daughters, but even slightly reduced it. In this case, one can think that the negative example of parents plays the role of a restraining factor, while heredity influences in the opposite direction.

Studies on adopted sons still more often show a significant correlation with biological parents in the development of alcoholism. Thus, regardless of the presence of alcoholism among caregivers, the frequency of alcoholism in adopted children whose biological parents are alcoholic remains constant. The values ​​for these two groups were 12.5 and 13.6%. Thus, it turns out that family influences did not play a significant role in this study! If one of the biological parents is sick with alcoholism, then the incidence among adopted children varies between 18-20% for sons and 2-10% for daughters. Estimates of incidence in the general population are 3-5% for men, 0.1-1% for women (extreme estimates are up to 10% for men and 3-5% for women).

Similar data are reported in a Danish study that analyzed the results of 55 adoptions of boys whose biological parents were an alcoholic. By the age of 30, 18% of adoptees had developed severe alcoholism (versus 5% in the control group).

Twin studies show considerable variation, but there is still a pattern. Although the variability of alcohol consumption within socially acceptable limits is weakly genetically determined, as we move from moderate consumption to excessive consumption, there is an increase in differences in the concordance of mono- and dizygotic twins. Thus, for the most severe manifestations of alcoholism, the concordance of monozygotic cases was 71%, and for dizygotic cases - only 32%.

Teenagers with a high risk of developing alcoholism (having alcoholics in the family) begin to drink alcohol earlier, and they begin to have problems with drug abuse at an earlier age. If they have first- and second-degree relatives who suffer from alcoholism, the likelihood of early onset of alcohol use increases, as does difficulty developing reading skills. These same adolescents (with a high risk of developing alcoholism) show the presence of certain neurobiological markers, in particular, a reduced amplitude of the component P 300 in evoked brain potentials. This is also indicated by a high score on the extraversion scale.

Another circumstance influencing alcohol abuse is the presence of genotype-environment interaction ( G E). The environment has different effects on the incidence of different types of alcoholism.

There are type I alcoholism, which is characterized by relatively moderate abuse, passive-dependent personality traits and minimal connection with crime, and type II alcoholism, which is characterized by an early onset, a tendency to commit violence and a connection with crime. Based on the morbidity data of close relatives, two genetic risk groups for these forms of alcoholism were selected and at the same time the conditions in which the subjects were raised were studied. It was found that in the case of the genetic risk group for type I alcoholism, the incidence of alcoholism is increased, i.e. a genetically determined cause of the disease is demonstrated, but at the same time, the incidence is influenced by the environment in which the subjects grew up. In an unfavorable environment that provokes alcohol abuse, the incidence of the disease is significantly higher than when brought up in a favorable environment. Thus, the effects of an unfavorable environment significantly enhance genetically determined tendencies.

In the case of the genetic risk group for alcoholism type II, the incidence is also increased, but it practically does not increase under conditions of exposure to an unfavorable environment. Thus, we have a case where the same environmental influence (upbringing in unfavorable conditions that provoke the onset of alcoholism) affects different genotypes differently. Environmental exposure increases the incidence of disease in some genotypes (with a genetic risk of alcoholism type I) and does not affect others (with a genetic risk of type II).

Another example indicating the presence of a genotype-environment interaction ( G E), given in a paper where it was noted that the heritability of alcohol consumption in married women is significantly lower than in unmarried women (this is typical for all ages). Religious upbringing has a similar effect on women (lower heritability values ​​for alcohol abuse). In these examples, environmental influences prevent genetically determined risk factors from manifesting themselves.

Experiments on animals have shown that the causes of alcohol preference are determined by the activity of alcohol-metabolizing enzymes. It seems that a similar pattern is typical for humans. Ethyl alcohol is converted to acetaldehyde by the enzyme alcohol dehydrogenase.

The next step is the conversion of acetaldehyde into acetic acid, which is carried out using aldehyde dehydrogenase. All unpleasant sensations that arise after drinking alcohol are not associated with the alcohol itself, but with an increased level of aldehyde in the blood. These are attacks of tachycardia (rapid heartbeat), flushing (hyperemia), sweating, increased blood pressure, the urge to urinate and other vegetative changes. Reduced activity of the enzyme aldehyde dehydrogenase leads to very unpleasant sensations, which, by the way, is the basis of one of the methods of treating alcoholism with the help of disulfiram (Antabuse), which inhibits the activity of this enzyme.

There is an allele (gene variant) ALDH 2*2, encoding the structure of aldehyde dehydrogenase with reduced activity. This atypical enzyme slows down the conversion of acetaldehyde to acetic acid. As a result, people with this variant of aldehyde dehydrogenase experience discomfort when drinking alcohol. In various European populations, the proportion of people with this variant of the enzyme ranges from 5 to 20%, but in Asia it is much more common (in 90% of Japanese). The presence of such a gene in a homozygous state (in approximately 50% of the East Asian population) is practically incompatible with alcoholism. In Japan, individuals homozygous for this allele (two copies ALDH 2*2), consume 10 times less alcohol per month than individuals whose genotype does not contain ALDH 2*2. If there is only one copy ALDH 2*2 monthly alcohol consumption is three times lower than in the absence ALDH 2*2 in genotype.

To separate the influence of heredity and cultural traditions in the development of alcoholism, one study compared the drinking patterns of white Americans and Asian Americans (whose ancestors immigrated to the United States long ago). The study was performed on college students. It turned out that 20% of Asian students and only 3% of white students do not drink alcohol at all. They use it less than once a month - 49 and 16%, respectively. Among those who drink alcohol almost every day, 35% were white and only 19% were Asian students. These findings indicate that cultural influences associated with “Western” cultural values ​​and lifestyles do not predict drinking patterns. At the same time, physiological features have a very noticeable effect. (14).

3.2 Smoking

There is a moderate genetic influence on smoking addiction. A study conducted in the USA on 4,775 couples showed that heavy and light smoking are determined by different genetic influences. One of the strongest genetic effects occurs in light smokers, and a completely different innate tendency is associated with severe tobacco addiction. (12).

3.3 Addiction

Due to the widespread availability of drugs today, drug addiction has become a serious social problem.

Addiction to different drugs has different genetic components. The heritability of susceptibility to heroin addiction is 50%, to psychedelic drugs 26%. Non-family environment has a large influence (53%) on the use of psychedelic drugs. It has been shown that one of the important factors of predisposition to drug addiction is such a psychological trait of a person as the search for novelty. (15).

Conclusion

Moving on to the description of quantitative traits, we found that all of them are controlled by genotype and environment (possibly with the exception of signs of brain asymmetry). Although it is quite easy to identify the genetic component of behavior in experimental animals, this is much more difficult to do in humans due to the complex interactions of genotype and external conditions. However, the behavioral traits that can be studied have a genetic component, even if it is difficult to detect. Based on this, we can say that genes control individual behavior to some extent, but the influence of the environment is also of great importance.

Therefore, behavioral genetics is now becoming particularly important for understanding biology, especially at the population and evolutionary levels.

WITHlist of literature

1. Aleksandrov A.A., Psychogenetics: Textbook. - St. Petersburg: Peter, 2007;

2. Anokhin A.P., Genetics, brain and human psyche: trends and research prospects. - M., 1988.

3. Antala F., Kaiger J., Modern genetics, Moscow, Mir, 199, T.1. With. 63-80;

4. Atramentova L.A. Introduction to psychogenetics: Textbook / L.A. Atramentova, O.V. Filiptsova. - M.: Flinta, Moscow Psychological and Social Institute, 2004.

5. Biological encyclopedic dictionary, M., 1989;

6. Human genetics: In 3 volumes / F. Vogel, A. Motulski; Per. from English edited by Yu.P. Altukhova, V.M. Gindilis. T. 3. - M.: Mir, 1990.

7. Gaito J., Molecular Psychobiology, trans. from English, M., 1969;

8. Kibernstern F., Genes and Genetics, Moscow, Paragraph, 1995;

9. Korochkin L.G. Genes and behavior // Soros educational journal. - 1997. - No. 1. - pp. 15-22;

10. Krushinsky L.V., Genetics and phenogenetics of animal behavior, in the book: Current issues of modern genetics, M., 1966;

11. Lobashev M.E., Genetics, Leningrad, Leningrad University Publishing House, 1967, p. 680-714;

12. Malykh S.B., Egorova M.S., Meshkova T.A., Fundamentals of psychogenetics. - M., 1988.

13. Mikheev V.F., Hereditary conditioning of some individual characteristics of human memory // Problems of genetic psychophysiology / Pod. ed. B.F. Lomova, I.V. Ravich-Scherbo. - M., 1978.

14. Moskalenko V.D., Poltavets V.I. Genetic basis of alcohol-dependent human behavior // Advances in modern genetics. - Vol. 17. - M.: Nauka, 1991.

15. Ravich-Shcherbo I.V., Maryutina T.M., Grigorenko E.L., Psychogenetics Aspect-press, 1999;

16. Ermon L., Parsons P., Behavioral genetics and evolution: - M.: Mir, 1984.

17. Yudin K.P., Genetics and life, 1979, M.

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Behavioral genetics, a branch of behavioral science that is based on the laws of genetics and studies the extent and manner in which differences in behavior are determined by hereditary factors. The main methods for studying genetic behavior in experimental animals are selection in combination with inbreeding (inbreeding), with the help of which the mechanisms of inheritance of forms of behavior are studied; in humans, statistical and genealogical analysis in combination with twin and cytogenetic methods. (5).

The dependence of behavior on hereditary factors - gene management and control of behavior - is studied at various levels of the organization of living things: in biocenoses, populations, communities, at the level of the organism, as well as at the physiological (organ, tissue, cell) and molecular levels. Research on the genetics of behavior has significant significance for the study of individual differences in higher nervous activity and identifying the relative role of congenital and individually acquired characteristics of behavior, for explaining the role of genetically determined characteristics of animal behavior in a population (for social animals - in a herd, flock, etc.), as well as for creating experimental models of nervous diseases.

Behavioral genetics is a relatively young field of knowledge, which took shape about half a century ago at the intersection of such disciplines as genetics itself, developmental biology and a complex of behavioral sciences, including psychology, ethology and environmental physiology. The task of this new direction was to study the ontogenesis of a broad class of biological functions of the body, called “behavior” and providing essentially two-way communication between the individual and his surrounding ecological and social environment. The global nature of this task in itself was the reason that the sphere of interests of behavioral genetics soon became involved in such widely separated areas of science and practice as endocrinology and psychiatry, biochemistry and pedagogy, neurophysiology and linguistics, anthropology and breeding of farm animals. In addition, since it has long become obvious that behavior is one of the most important factors in the evolutionary process, the genetics of behavior in recent years has become more and more closely linked with evolutionary teaching, becoming an integral part of modern evolutionary biology.

Genetic analysis of animal behavior

Genetic research in humans has a number of understandable limitations. In this regard, studies of the genetic basis of behavior in animals are of interest. Here you can use selection methods, obtaining inbred lines, modern methods of genetic engineering, selectively turning off certain genes, causing mutations, etc. Inbred lines obtained through long-term inbreeding (at least 20 generations) represent animals identical in genotype, therefore all differences that can be observed among animals of the same line are associated with environmental influences.

Genetics of insect behavior

Let us give an example of genetic analysis of behavior, which is quite often discussed in educational literature. We'll talk about bees and a disease called American larval rot. There is a line of bees that are resistant to this disease because if the disease occurs, the bee larvae will immediately unseal the cell they are in and remove it from the hive. This prevents the spread of the disease, and resistance to it is associated with characteristic behavior! When bees that are resistant to the disease are crossed with those that are not resistant, first generation hybrids (F1) are obtained that do not clean the hives. It is clear from this that the allele or alleles causing this type of behavior are recessive. The first generation F1 hybrids are again crossed with resistant bees (the so-called analytical crossing - with recessive homozygous individuals). As a result, the offspring exhibit four variant phenotypes in a 1:1:1:1 ratio. These are the options:

– bees open the cells and remove the affected larvae;

– open the cells, but do not remove the affected larvae;

– do not open the cells, but remove the affected larvae if the experimenter opens the cell;

– do not open the cells, do not remove the affected larvae.

Thus, it is obvious that this rather complex behavioral act is controlled by genes at only two loci. One allelic gene determines the actions of opening the cell, the other is associated with the removal of the affected larva.

In this case, it is impressive that quite complex actions can be controlled by just one gene.

Fruit flies - Drosophila, which have been a favorite subject of geneticists for many years - have been identified with a huge number of mutations affecting behavior. Yes, mutation dunce leads to disruption of the ability to develop conditioned reflexes. There are several known mutations that somehow impair learning. It is important that all these defects are associated with impaired metabolism of so-called second messengers (primarily cyclic AMP), which play an important role in intracellular signaling and synaptic plasticity.

There are mutations that lead to high and low sexual activity, to the avoidance of certain odors, changing motor activity, even to the point that there is a mutation that determines how the Drosophila folds its wings - right over left or vice versa.

Sometimes there are examples of very specific behavioral deviations. So, with mutation fru(from fruitless– infertile), the following disturbances in sexual behavior are observed in males: they do not court females, but only court males homozygous for this mutation, and stimulate normal males to court themselves. The result was something like a model for the formation of homosexual behavior.

In general, one gets the impression that most behavioral acts in Drosophila are genetically predetermined in every detail.

Animal learning studies

One of the most important properties of animal behavior is the ability to learn. Animal research provides an opportunity to conduct breeding experiments. Tryon was one of the first to conduct such an experiment on rats. He carried out selection based on the learning ability of animals, which had to find the correct path to feeding placed in a complex 17-dead-end maze. Animals that were good and poorly trained were selected and subsequently crossed only with each other. Regular selection gave a very quick result - starting from the eighth generation, the learning indicators of “smart” and “stupid” rats (the number of erroneous runs in the maze) did not overlap. Selection was carried out until the 22nd generation, as a result of which two groups of rats were obtained - well trained ( bright) and bad – ( dull). Under the same growing and testing conditions, differences between these groups are due only to differences in genotype.

Subsequently, many strains were obtained, especially in mice, differing in their ability to perform various forms of learning. Similar lines were selected for their ability to learn in the T-maze, for learning active and passive avoidance, and swimming in the Morris water test. Sometimes the task an animal performs is quite complex. For example, strains of mice were obtained that were good and bad at learning the food-procuring motor conditioned reflex. The mice were reinforced when they jumped in response to a sound or light stimulus onto different shelves. In this case, some community patterns can be noted:

1) there is usually a large variation of the trait in the source population;

2) Although the selection response can appear very early, and the difference between lines is detected after 2–3 generations, it takes much more generations (about 10–20) for stable significant differences between lines to appear.

The high spread of initial values ​​of the trait and the gradual development of the selection response are evidence of the polygenic nature of the trait. In other words, the manifestation of this trait in the phenotype depends on a relatively large number of genes. The same is true for most mammalian behavioral traits.

There is another problem associated with selection experiments. Selection is carried out when testing a specific task. Naturally, the question arises: to what extent does the ability to solve this problem correlate with the ability for other types of learning? There is no clear answer to this question.

For example, when they began to study in more detail the ability to learn in general on lines of rats obtained by Tryon ( bright And dull), it turned out that those who were well trained ( bright) learn food-procuring behavior faster, and rats dull in turn, demonstrate better performance in defensive reaction tasks. Thus, here the problem of learning can be transferred to the plane of motivational mechanisms. It is known that motivation can have an extremely strong impact on learning outcomes.

It turns out that the rat line bright are more motivated by hunger, while rats dull are more motivated by fear in threatening situations. Just like motivation, the success of learning can be influenced by sensory abilities, the level of motor activity, and the emotionality of animals. Accordingly, genes that influence the activity of these qualities can have an impact on learning.

However, some lineages also show differences in more general learning abilities. So, mouse lines DBA/2J learn better than animal lines C.B.A., which is confirmed in a number of tests: during food reinforcement in the maze, in the shuttle chamber during the development of a conditioned reflex reaction of active avoidance, during operant learning. This means that there are certain genetically determined properties of the nervous system that affect the ability to implement various types of learning. The list of mutations that impair learning and memory in mice is rapidly expanding.

Table 1. Mouse genes localized on certain chromosomes and playing an important role in learning and memory

Differences in memory characteristics were also noted in Tryon's rats, which certainly affected the test results. So, it turned out that rats have lines bright consolidation occurs faster - strengthening of memory traces, their transition into a stable form. You can resort to influences that disrupt short-term memory, for example, using a special form of electric shock that causes amnesia. It turned out that already 75 s after training, electroshock amnesia cannot be induced in rats of the line bright, whereas on the rat line dull The electroshock procedure still has an effect.

Different speeds of consolidation appear to determine differences in the success of forming orientation skills in a maze. What happens if rats line dull will you be given enough time to memorize? Studies have shown that when the intervals between trials were 30 s, rats bright learned much faster than line rats dull, as it should have been. But when the interval was increased to 5 minutes, the difference in learning between the lines decreased significantly. If the rats were given only one trial per day, the learning performance of both strains became identical. The speed of skill acquisition and the speed of consolidation can be determined by different mechanisms!

An important conclusion: selection of learning conditions can reduce or even eliminate differences in genetically determined abilities.

Currently, a number of mouse strains have been obtained that differ sharply in the speed of memory consolidation. There is a line ( C3H/He), in which learning is possible only through continuous training. There is a line ( DBA/2J), in which training, on the contrary, is much more successful when the intervals between individual training sessions increase. And finally, the line (BALB/c) was introduced, for which the nature of the intervals between experimental sessions does not affect the learning results. This approach thus creates unique opportunities for studying memory mechanisms.

Another area of ​​animal research is to elucidate the influence of the environment on the formation of behavioral properties. Let's go back to line rats again bright And dull. You can conduct an experiment to raise these rats in different conditions. One group (control) is grown under normal vivarium conditions. For the other, an “enriched” environment is created - large cells with painted walls, filled with various objects, mirrors, swords, ladders, stairs, tunnels. Finally, the third group is provided with an “impoverished” environment, where the influx of sensory stimuli is severely limited and the possibilities for search and exploratory activity are limited. In graph 1, the enriched environment is designated as “good” conditions, the depleted environment as “bad”. Normal conditions correspond to the control group.

Graph 1. Results of training in a maze of lines of “smart” and “stupid” rats raised in deteriorated, normal and improved conditions. (15).

The results of the control group correspond to expectations - rats of the line bright when learning in a maze, they make much fewer mistakes compared to rats of the line dull. However, for rats raised in an enriched environment, this difference practically disappears, mainly due to a sharp decrease in errors in the “stupid” strain of rats. In the case of rearing in a depleted environment, the difference between the two lines also disappears, and this time mainly due to a sharp increase in the number of errors in the “smart” line of rats.

Here we touch upon a very important problem - the existence of powerful mechanisms of plasticity of the nervous system that are capable of compensating for very significant defects. Numerous studies on raising rats in an enriched environment have shown that relatively quickly - within 25-30 days - very significant morphological differences arise at the level of the cerebral cortex. Animals kept in an enriched environment have a thicker cortex, larger neuron sizes, and a 10–20% increase in the number of dendritic processes per neuron. All this leads to a 20% increase in the number of synapses per neuron. Ultimately, we are talking about billions of new synapses, which dramatically increases the capabilities of the nervous system. Particularly important is the fact that this plasticity potential is maintained almost all the time. Experiments on adult animals led to similar results. Similarly, an enriched environment has an impact on a child’s development.

Video: About the influence of genetics on behavior and character.


Chromosome	Learning and Memory

BEHAVIOR GENETICS- a branch of genetics devoted to the study of patterns of hereditary conditioning of functional manifestations of the activity of the nervous system. The main task is to describe the mechanisms of implementation of genes in behavioral traits and highlight the influence of the environment on this process.

Along with other research methods, the genetic selection method is used here, thanks to which the properties of the nervous system and behavioral characteristics can be purposefully changed.

Each heritable behavioral trait usually has a complex polygenic character. Animals from lower levels of the evolutionary ladder (insects, fish, birds) are characterized by low variability in innate, instinctive actions determined by genotype. With evolutionary development, the process of formation of conditioned reflexes becomes increasingly important, and the genotype determines phenotypic variability less and less.

Information important for adaptation is not only acquired in one’s own experience, but can be transmitted from parents to offspring through direct contacts, due to imitative conditioned reflexes.

Data obtained in the genetics of behavior are of particular importance for the study of human nervous activity in pathologies: often mental retardation and mental illnesses are hereditary and associated with genetic disorders.

BEHAVIOR GENETICS(English)

Behavioral genetics) is a section of genetics that studies the patterns of hereditary determination of the structural and functional characteristics of n. With. G. p. allows us to understand the nature of the hereditary transmission of behavioral characteristics; reveal the chain of processes unfolding in ontogenesis leading from genes to traits; isolate the influence of the environment on the formation of behavior within the potential capabilities specified by the genotype.

Using the genetic selection method, the properties of n. s.and behavioral features m.

b. directionally changed. The inheritance of differences in behavioral traits is, as a rule, complex polygenic in nature.

It has been experimentally shown that the species stereotype of animal behavior has a very strict hereditary conditionality.

Low variability of innate, instinctive acts is especially characteristic of animals standing at lower levels of the evolutionary ladder - insects, fish, birds, but even in insects the behavior is m.

b. modified due to the development of temporary connections. Moreover, behavior is not a simple result of evolutionary changes; it plays an active role in evolution, since through behavioral adaptations the effect of selection is manifested in the animal population and the regulation of its structure and numbers is ensured.

Hereditary information from parents to descendants can be transmitted on the basis of direct contacts, through the development of imitative conditioned reflexes and other ways of perceiving and transforming information (i.e.

n. signaling heredity).

Of particular importance for genetic research is the study of human nervous activity—in normal and pathological conditions. Often mental retardation and mental illnesses have a hereditary etiology associated with genetic metabolic disorders, changes in the number and structure of chromosomes, etc.

disorders of the genetic apparatus.

behavioral genetics

See Psychogenetics. (I. V. Ravich-Scherbo.)

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Lecture 3. 1. Innate forms of behavior

1. Innate forms of behavior

2. Acquired forms of behavior

The adaptation of animals, in the processes of evolution, to relatively constant phenomena and those that are periodically repeated in the external environment, has developed in them genetically fixed, innate forms of behavior.

At the same time, adaptation to fickle, unstable environmental conditions forms in each generation of animals dynamic forms of behavior that are acquired throughout ontogenesis.

Congenital Behaviors

At different stages of evolution, the following innate adaptive reactions can be distinguished: taxis, reflexes and instincts.

Taxis are the simplest form of behavior that determines the interaction of an organism with the external environment in unicellular and multicellular organisms.

Taxis in ethology is called oriented (directed) movement, which is connected with some complex of fixed actions.

For example, when a greylag goose rolls a deflated egg toward the nest, it performs lateral movements that are designed to hold the egg under its beak. These directed movements represent taxis. At the next stages of evolution, the role of taxis sharply decreases and they are replaced by other, more advanced adaptation mechanisms.

Reflexes are also a type of adaptive behavior. In this case, we consider an innate unconditioned reflex reaction, which serves as one of the main types of adaptation in the animal world.

For example, a chicken that has just hatched from an egg begins to peck, and a calf begins to suck.

Instinct (from the Latin “instinctus” - impulse) is a set of innate stereotypical acts of behavior characteristic of individuals of a given species under certain conditions.

Examples include food, imitation, herd, play (in young animals), and migration.

Each such instinct can also include simpler instinctive acts. For example, releasing chicks from the nest, pecking grain, babies sucking milk, and tentatively exploratory reactions.

Instinctive behavior, like all other forms of behavior, has a certain direction - the preservation and development of the organism in conditions characteristic of the life of this species of animal.

According to the teachings of I.P. Pavlov, in the physiological understanding, instincts are chains of complex unconditioned reflexes fixed by evolution, which include compelling and reinforcing reflex links.

In other words, the most complex unconditioned reflexes (for example, nest-building, play, etc.) are represented not by one reflex arc, but by a whole complex of unconditioned reflex reactions.

This complex includes all genetically determined mechanisms necessary for the formation of appropriate acts of behavior: the mechanism of formation of metabolic needs, the mechanism of biological motivations, the mechanism of foresight and evaluation of results, the mechanism of achieving goals (K.V. Sudakov).

Obviously, all mechanisms cannot be formed at the time of birth. Some of them (for example, sexual motivation) are formed in the processes of ontogenesis, as morphofunctional and endocrine systems form and mature.

Coordinated movements of the wings of birds during flight do not immediately arise: this habit depends on learning.

To student I.P. Pavlova to academician L.O. Orbeli has a reasoned concept of postnatal maturation of unconditioned reflexes under the influence and interaction with conditioned ones. For example, building a nest in a rat is an innate chain reflex, but it can be destroyed by raising the rat in a cage with a slatted floor, where the animals’ attempts to collect materials for building a nest have previously ended in failure (P.V.

Simonov). The innate chain reflex of hatching eggs does not manifest itself when chickens are kept in cages.

In our time, the view of the exclusively genetic nature of instincts has changed. Genes cannot determine the course of ontogenesis regardless of the environment.

So, be - what types of behavior are the result of genetic and environmental interactions.

Instinct also needs “training,” which is illustrated by the presence of so-called imprinting.

Instead of the term “instinct,” the expression “innate forms of behavior” is now predominantly used, emphasizing only their relative independence from environmental influences.

In the implementation of acts of behavior based on the innate reactions of animals, the structures of the diencephalon (hypothalamus) and the limbic system play an important role. Thanks to them, behavioral reactions are adaptive, adaptive in nature and are able to maintain biochemical and metabolic homeostasis.

Acquired Behaviors

Acquired forms of behavior include learning and mental activity.

Learning is the process through which life experiences influence the behavior of each individual, and allows animals to develop new adaptive reactions taking into account past experiences, as well as change those reactions that turned out to be non-adaptive.

At the same time, the behavior of animals becomes more flexible and adaptive. As the research of I.P. Pavlov showed, the basis of learning is the formation of conditioned reflexes.

The conditioned reflex is the main form of learning. A conditioned reflex is an adaptive reaction of animals that occurs through the formation of temporary nervous connections between two excitation centers in the cerebral cortex: the center of conditioned and the center of unconditioned stimuli.

The conditioned reflex is a functional unit of activity in the higher parts of the brain.

Two types of conditioned reflexes can be distinguished: the first type is the classical Pavlovian conditioned reflex, the second is the operant (instrumental) conditioned reflex.

Both of them are reproduced in laboratory conditions. In the first case, the animal’s reaction to a conditioned stimulus recreates an unconditioned reflex (secretory or motor), and in the second case, movement, which is a necessary condition for reinforcement. For example, the call is not reinforced with food every time, but only if the animal presses the lever. An example of an instrumental conditioned reflex is the process of drinking water from a drinking bowl.

The animals press the valve with their muzzle, water flows into the drinking bowl and the animals drink. In this reflex there are causal-hereditary relationships, and the fact of unconditional reinforcement depends on the animal itself.

Conditioned reflex learning of both types is associative learning, i.e. such that it arises as a result of the formation of connections in the brain, which can be modified or destroyed when the living conditions of the individual change.

There are also non-associative forms of learning, which include: habituation, latent learning, imitation, trial and error, imprinting, insight.

addictive- the simplest form of behavior - it does not consist in identifying a new reaction, but in losing the one that existed before.

If animals are offered a stimulus that is not accompanied by reinforcement or punishment, then gradually the animals stop responding to it.

For example, birds gradually stop paying attention to a scarecrow that forces them to fly away when it is first placed on the field. Phenomena similar to addiction are found in any group of animals, starting with the simplest, all typical properties of addiction can be found at the level of individual neurons and neuromuscular connections.

Habituation is one of the important processes of adaptation of animal behavior to living conditions. Habituation will also play an important role in the development of behavior in young animals, which are often threatened by various predators (they quickly learn not to respond to foliage when they are moved by the wind and other neutral stimuli).

The innate pecking reaction in newly born chicks is initially directed at any small object, but then habituation to unnecessary objects occurs.

Latent learning according to Thorpe's definition, it is the formation of a connection between indifferent stimuli or situations without explicit reinforcement.

Latent learning, in its natural form, is often the result of animals' exploratory activity in a new situation. In the process of exploring conditions, animals accumulate information about them.

2.10. Behavioral genetics

The life of a small animal or bird when a predator attacks it depends on detailed knowledge of the geography of the area where it lives. Information about the environment can later be used in the processes of searching for food or a sexual partner.

Numerous insects carry out a special “reconnaissance flight” during which they record the position of the site relative to the Sun and the outskirts.

Thus, bees during a reconnaissance flight, which lasts 1-2 minutes, remember the new location of the hives.

Imitation (inheritance)- one of the forms of training.

The learning of species songs by birds is based on imitation. Through imitation, young farm animals learn to master many necessary exercises and habits, for example, the ability to graze. When cows are kept in boxes, a newborn calf, imitating a cow, quickly gets accustomed to eating roughage.

Trial and error method– a complicated reflex in which problems are solved as a result of a blind search.

This type of learning was studied by E. Thorndike through the use of a variety of “problem chests”. The latter were a cage that could be opened from the middle only by pressing a lever or pulling a ring. A cat placed in such a cage makes an attempt to escape; it runs around the cage without stopping until after some time it accidentally tugs at the ring. After the second and third attempts, the cat concentrates its attention on the lever, and as soon as it is locked, it rushes to the ring and fiddles with it.

Trial and error learning is often observed in changes in animal behavior that involve searching for food, storage, or a sexual partner.

As a rule, this process is accompanied by the formation of conditioned reflexes of the first order, since both new stimuli and new behavioral reactions must be remembered.

Trial and error, reliably, is the category that is most suitable and to which the formation of new motor exercises can be attributed. Young mammals and birds, for example, improve the coordination of their movements through training, playing with their parents and among themselves.

Rice. 6. The goslings are watching Konrad Lorenz.

Imprinting was first described by K. Lorenz in 1937 in birds. Imprinting is also observed in sheep, goats, deer, horses and other animals, whose babies are able to move immediately after birth. Imprinting is observed in the reactions of newborn animals following a moving object. Imprinting is a special form of learning that has much in common with conditioned reflex learning, although it is tuned not to individual, but to species characteristics. It is formed only in the early stages of postembryonic development. Thus, in his experiments, Lorenz forced broods of goslings, who mistook him for their mother, to follow him (Fig. 6).

Similar phenomena are observed in mammals. The human-raised lambs follow her and show no curiosity about other sheep. Scott and Filler summarized the results of substantial research in dogs. They found that between three and ten weeks of age, dogs have a sensitive period during which puppies form normal social interactions.

Puppies isolated for more than 14 weeks do not subsequently respond to their relatives, and their behavior is completely abnormal.

Insight- the most important degree of acquired behavior.

This behavior is based on understanding. It occurs predominantly in the most developed representatives of chordates - primates. A classic example of insight in animals is provided by Keller's early experiments on chimpanzees. When several bananas were clinging very high, and the monkeys were unable to reach them, they began to stack boxes one on top of another, or inserted sticks one into another so that they could climb higher and knock the bananas to the ground.

More often, they arrived at such a decision entirely unexpectedly, although they used previous experience of playing with boxes and sticks (latent learning), and the monkeys needed a significant period of trial and error to build a stable pyramid of boxes. Elements of mental activity often appear in the behavior of anthropoid apes and other primates. Numerous dog owners give examples of their dogs doing smart things.

Insight can be seen as a manifestation of the ability to think creatively.

Thinking- the highest form of behavior that dominates in a person. Higher animals have a proven presence of elementary mental activity. An example would be insight. Sometimes, after a series of unsuccessful attempts and a pause, which then comes, animals unexpectedly change the tactics of their behavior and solve the problem. So, in the brains of the animals, an assessment of previously carried out attempts occurred, and adjustments were made to the plan of further actions.

In higher animals, elements of mental activity exist and develop in evolutionary terms. This accounts for the ability of animals to solve complex problems. So, in the animals’ brains an assessment was made of earlier attempts and adjustments were made to the plan for further actions.

In higher animals, elements of mental activity exist and develop in evolutionary terms. This involves animals solving complex problems. The considered forms of complex behavior - learning and thinking - arise at the highest stages of evolution.

Learning becomes dominant in mammals. Their behavior is determined by reactions that are innate and acquired as a result of learning.

Lecture 3

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Variation due to genetic factors

Variation due to genetic factors is complex, but if it is significant and known, it can be used to calculate the possible gain for certain tree characteristics.

Genetic variation can be divided into two main components: additive And non-additive. If we imagine this in statistical terms, then genetic variance consists of additive and non-additive variance components.

The additive component of variance is the variability caused by the combined action of alleles of all gene loci that affect the characteristic. Non-additive genetic variation can in turn be divided into two parts: dominant And epistatic. Dominant variance is caused by the interaction of certain alleles located in one gene locus, while epistatic dispersion is caused by the interaction between genes of different loci.

This concept will be discussed in more detail later.

Here it is enough to note that the additive part is one of the most important in programs for selective improvement of populations.

Non-additive variation can be used in other, more specialized programs that involve making specific crosses or using vegetative propagation for commercial purposes. In most genetic breeding improvement programs, non-additive genetic variation usually receives less attention because the additive portion of the genetic variance can be more easily exploited.

Most characteristics of economic importance are, to one degree or another, under the control of the additive component of genetic variability (V.

Zobel, J. Talbert, 1984). This is important because additive variance can be successfully used in simple breeding systems. The qualitative characteristics of wood, such as density, straightness of the trunk and others, are determined to a greater extent by additive dispersion than growth characteristics.

Although growth performance is controlled to some extent by additive genetic influences, it is also significantly influenced by the nonadditive variance associated with it. Therefore, any breeding program must include testing of the progeny of selected phenotypes to determine the true genetic value of the trees.

The response to selection for characteristics with significant non-additive variance, such as height, is significantly less satisfactory than the response to selection for quality characteristics, which are usually under stricter genetic control of the additive component of variance.

With regard to the characteristics of adaptation, it can be noted that this question has not yet been fully clarified.

However, available evidence favors inheritance of these characteristics in an additive manner. This suggests that any outstanding gains obtained for the improved characteristics of trees that grow satisfactorily in extreme or sub-extreme habitat conditions can be retained.

By selecting trees with outstanding characteristics that grow better in these conditions, and then using their seeds, one can expect to afforest such areas with trees with the desired economically important traits.

Pest resistance includes both additive and non-additive variance depending on the insect and tree species. But usually good results are possible when using the additive part of genetic variability in breeding programs.

The above principles should be used by breeders at the beginning of their work on a particular breeding program.

The first stages of work should involve determining the amount and type of variation in source natural or cultivated populations so that they can then be used in an intelligent manner.

Section 1. General issues of behavioral genetics.

Controlling environmental influences allows for better use of genetic variation.

To identify and use genetically determined variability, certain crossing or mating systems are most often used (matting systems). The type of crossing system within a species has the main influence on the variability of the studied samples.

Cross pollination (outcrossing), which is most characteristic of most species of forest woody plants, as a rule, produces highly variable (heterozygous) populations in genetic terms.

In cross-pollination, different genotypes successfully hybridize with each other, and only a small proportion of crosses occur between female and male organs of the same plant or between closely related individuals.

If the latter occurs, i.e., pollen from a tree or a given genotype pollinates its own female flowers, we speak of self-pollination (selfmg). The same thing happens if pollination occurs between ramets of the same clone.

Even if the ramets (grafts, root suckers, etc.) are separate plants, they are genetically identical.

Therefore, when creating forest seed plantations, care should be taken that grafting trees (ramets) of the same clone are not planted in close proximity to each other.

It should be noted that cross systems support a high degree of genetic variation, while in selfing systems genetic diversity is significantly reduced.

As a rule, growth vigor also decreases significantly when inbreeding occurs, i.e., as if there is a return from the hybrid to the original growth vigor.

This or that degree of relationship is characteristic of natural plantings. For this reason, it is recommended to take only one selected best tree from a stand to create forest seed plantations in one place.

Degrees of relationship can be very diverse. For forest woody plants, little is known about the effects of siblings or other inbreeding.

However, their adverse effects have been well studied in crop plants and are therefore recommended to be avoided. The most common phenomenon is a decrease in sperm production, although there were exceptions when during the mating of half-sibs and even full-sibs such a phenomenon was not observed. But what was common was not only a decrease in seed production, but also a decrease in germination during self-pollination.

When viable seedlings were obtained, they often had poorer growth (Ericsson et al, 1973 - cited by B. Zobel, J. Talbert, 1984). The unfavorable consequences of self-pollination were noted even earlier (A. S. Yablokov, 1965; E. Romeder, G. Shenbach, 1962, etc.; see also chapter).

The results of studying self-pollination in various species of coniferous and deciduous trees showed that the following consequences may occur (B. Zobel, J.

Talbert, 1984; Yu.N. Isakov, V.L. Semerikov, 1997, etc.):

1. No healthy seeds are formed.

2. Seeds are formed, but they do not form shoots.

3. The seeds are viable, but the seedlings are abnormal and often live only a short time and then die.

4. Seedlings survive, but they are small, weak, often with yellowed leaves and slow growing. Some of them can be diagnosed and removed at the nursery stage, before planting in a permanent place.

Seedlings grow more slowly than normal trees, but this is not noticeable enough to remove them at the nursery stage. Their further cultivation is undesirable, since they produce less wood than seedlings obtained from cross-pollination.

6. Seedlings grow as well, and sometimes even better, than those obtained from cross-pollination. Self-pollinating trees, the offspring of which grow as well as those from cross-pollination, are very rare.

All this suggests that when creating forest seed plantations, it is necessary to first study the source material and the possibility of using it in cross-pollination or self-pollination systems.

The use of inbred lines, subsequently cross-crossed, has been proposed as a breeding system.

This method is widely used in agriculture. However, it has been little practiced in breeding programs for forest tree species for several reasons: low seed productivity of self-pollinators, low vigor of inbred offspring, and a significant decrease in wood supply in breeding populations.

In general, based on the materials in this section, it should be noted that genetic variability, a very important aspect of breeding programs, can be significantly increased through intralocus and interlocus interactions, mutations, migrations and other evolutionary factors.

These phenomena will be discussed in more detail in the subsequent presentation.

Behavioral genetics: When behavior is influenced by genes.

Researchers were able to discover that some character traits, including female intuition, are hereditary. In the wake of interest in “scientific predictions”, psychogenetics has gained popularity - a science that studies the interaction of heredity and the characteristics of human character and behavior.

It's hereditary for you

Psychogenetics appeared in the second half of the 19th century. The first person to study the hereditary nature of behavior was Darwin's cousin, Francis Galton. He wrote many works on the inheritance of mental abilities and talent. Moreover, the term “genetics” itself appeared two years before his death in 1909. Modern psychogenetics uses several methods. First of all, this is the study of the behavior of twins, the genealogical method, as well as the method of adopted children, when the child’s character traits are compared with the character of biological and adoptive parents.

It should be understood that genes do not determine a human character trait as such. Genes are responsible for the synthesis of one or another type of protein, which in turn can either influence nerve centers or change the concentration or action of other substances in the human brain.

Human behavior, like many other characteristics, depends not only on genetics, but also on external factors. Thus, the gene for a predisposition to emphysema may never manifest itself if its carrier has never smoked in his life and lived in a mountainous area with clean air.

In their articles entitled “A gene has been found...” journalists quite often forget to explain that traits in most cases are determined by a combination of genes, and such a complex component of a person as behavior depends to a large extent on the nervous system.

However, something has already been found out.

Infidelity. University of Georgia researchers have discovered that a mutation in the gene that responds to the synthesis of vasopressin receptors leads to polygamous behavior in vole mice. Males with a particular form of the gene constantly changed females and rarely stayed with each for long. Scientists injected vasopressin receptors into the frontal lobe of a polygamous mouse - the results exceeded all expectations.

The former playboys dramatically changed their behavior and immediately chose a permanent companion. The researchers suggested that the fact of fidelity is explained by the level of pleasure that the male experiences when communicating with the female. The more receptors, the stronger the pleasure, and the less reason to look for a new girlfriend.

Courtship. This gene was discovered simultaneously by Austrian and American scientists. During the study, it became apparent that the presence of this gene causes males to court females. When the gene was introduced into the DNA of female fruit flies, they began to behave like males: pester and sexually dominate. At the same time, its removal from the DNA of males deprived them of the desire to court females.
Loneliness. Scientists from the University of Amsterdam and the University of Chicago have concluded that the tendency to loneliness has a genetic basis. More than eight thousand twins took part in the survey and answered questions like “I lose friends quickly” or “no one loves me.” The researchers found that identical twins had more similar responses than fraternal twins.

Female intuition. In fact, we are talking not so much about intuition as about the ability to independently recognize social norms of behavior. A gene was discovered on the X chromosome that improves the perception of non-verbal information in women, so they quickly navigate the value system. This, according to scientists, is a manifestation of female intuition. Men, in turn, perceive nonverbal information much worse, and they have to be taught norms of behavior.

Infidelity. Scientists have noticed that if one of the twin sisters cheats on her husband, then the probability that the second will take a lover is 55%. This result was confirmed when comparing data from identical and fraternal twins.

Altruism. Experts at the Hebrew University of Jerusalem recently concluded that people do not become altruists out of the kindness of their hearts. Scientists have discovered that a mutation in a specific gene reduces the number of vasopressin receptors in certain areas of the brain. This leads to the fact that a person experiences much less pleasure when performing good deeds. The leader of the group, Richard Ebstein, suggested that the cruel and selfish behavior of some people is explained by the fact that they simply do not receive a “reward” from their brain in the form of pleasure for altruistic actions.

Aggression. Many studies have shown that aggression, high levels of anxiety and problem behavior in adolescents can be determined by gene mutations that change the level of serotonin or monoamine oxidase A. Researchers from King's College London found that some juvenile delinquents are carriers of a certain form of the gene. It causes monoamine oxidase deficiency, which (combined with poor nutrition in childhood) greatly increases the likelihood of antisocial behavior in adolescents.

Gene found: what to do with it?

Psychogenetics has a lot of ethical problems. As research like this increases, people with certain personality traits or tendencies may be subject to discrimination. For example, potential offenders may be forced to undergo mandatory corrective treatment. Several scientific papers have already appeared that claim the genetic nature of homosexuality, and this has divided the scientific community into two parts. Some believe that revealing the hereditary nature of homosexuality will lead to greater tolerance towards gays. Others, and they are now the majority, agree that society will begin to perceive homosexuality as a disease, and attempts will again be made to “cure” all gays, which will lead to a serious split in society.

The most negative consequence of the development of modern psychogenetics may be the emergence of a new round of eugenics: the process of improving the gene pool. There are fears that women will become more likely to have abortions if tests show that the child, for example, has little chance of becoming an intellectual. China has already faced a similar problem: with the introduction of the “one child per family” rule, women terminated their pregnancies if an ultrasound showed a girl. In 2006, the country's authorities officially banned sex determination during pregnancy because the population ratio had begun to shift toward males.

And yet, everyone who hopes that the achievements of psychogenetics can make their lives easier or shed light on abilities with which “nothing can be done” must remember one fundamental thing. Even if we have a certain gene in our DNA, external factors can either “turn it on” or “turn it off,” so much in our lives still depends only on us.

Natalia Rostovtseva