Phenotype and genotype - their differences. What are genotypes? The importance of genotype in the scientific and educational spheres

In genetics there are two very important concepts. These are concepts genotype And phenotype. We already know that the hereditary constitution consists of large number various genes. The entire set of genes of a given organism is called its genotype , that is, the concept of genotype is identical to the concept of genetic constitution. Each person receives his own genotype (set of genes) at the moment of conception and carries it without any changes throughout his life. The activity of genes may change, but their composition remains unchanged.

From the concept genotype Another similar concept should be distinguished - genome. Genome is a set of genes characteristic of the haploid set of chromosomes of an individual of a given species. Unlike the genotype, the genome is a characteristic of a species, not an individual.
Phenotype represents any manifestations of the organism at every moment of its life. The phenotype includes appearance, and internal structure, and physiological reactions, and any forms of behavior observed at the current moment.

For example, the already mentioned blood groups of the AB0 system are an example of a phenotype at the physiological and biochemical level. Although at first glance it seems to many that the blood type is a genotype, since it is clearly determined by the action of genes and does not depend on the environment, it is only a manifestation of the action of genes, and therefore should be classified as a phenotype. Let us remember that representatives of blood groups A or B can have different genotypes (homozygous and heterozygous).

All behavioral manifestations are complex phenotypes. For example, the handwriting that distinguishes a given individual is his behavioral manifestation and also belongs to the category of phenotypes. If the blood type does not change throughout life, then handwriting undergoes significant changes as writing skills are trained.

If genotypes are inherited and remain unchanged throughout the life of the individual, then phenotypes for the most part are not inherited - they develop and are a consequence of our genotypes only to a certain extent, since big role conditions play a role in the formation of phenotypes external environment.

The entire process of development from a fertilized egg to an adult organism occurs not only under the continuous regulatory influence of the genotype, but also under the influence of many different environmental conditions in which the growing organism finds itself. Therefore, the extraordinary variability inherent in living organisms is due not only to the enormous diversity of genotypes arising from the recombination of genes and the mutation process, but is also largely explained by the fact that individual individuals develop in different environmental conditions.

For a long time there has been controversy about what is more important for the formation of an organism - the environment or the genetic constitution. Particularly heated debates flare up when it comes to human behavior, his psychological characteristics - temperament, mental abilities, personality traits. It is no coincidence that it was with the question of the nature of mental talent that research in the field of human genetics began. F. Galton was the first in a scientific treatise to put two concepts side by side, which in one form or another do not leave the pages scientific literature to the present day. These concepts are “nature and nurture”, that is, “the nature and conditions of upbringing”.

Geneticists, and behavioral geneticists in particular, are often accused of denying the role of the environment. However, such a reproach is completely unfounded. One of the main postulates of genetics is the thesis that phenotype is the result of the interaction of genotype and environment. In the process of this interaction, the diversity of phenotypic manifestations arises, which is characteristic of most human traits that belong to the category of quantitative and form a continuous series of variability.

Phenotype

Phenotype(from Greek word phainotype- manifest, discover) - a set of characteristics inherent in an individual at a certain stage of development. The phenotype is formed on the basis of the genotype, mediated by a number of external environmental factors. In diploid organisms, dominant genes appear in the phenotype.

Phenotype is a set of external and internal characteristics of an organism acquired as a result of ontogenesis (individual development).

Despite its seemingly strict definition, the concept of phenotype has some uncertainties. First, most of the molecules and structures encoded by genetic material are not noticeable in the external appearance of the organism, although they are part of the phenotype. For example, this is exactly the case with human blood groups. Therefore, the expanded definition of phenotype should include characteristics that can be detected by technical, medical or diagnostic procedures. A further, more radical extension could include learned behavior or even the organism's influence on the environment and other organisms. For example, according to Richard Dawkins, beaver dams, like their incisor teeth, can be considered a phenotype of beaver genes.

Phenotype can be defined as the “carrying out” of genetic information towards environmental factors. To a first approximation, we can talk about two characteristics of the phenotype: a) the number of directions of removal characterizes the number of environmental factors to which the phenotype is sensitive - the dimension of the phenotype; b) the “distance” of removal characterizes the degree of sensitivity of the phenotype to a given environmental factor. Together, these characteristics determine the richness and development of the phenotype. The more multidimensional the phenotype and the more sensitive it is, the further the phenotype is from the genotype, the richer it is. If we compare a virus, a bacterium, an ascaris, a frog and a human, then the richness of the phenotype in this series increases.

Historical reference

The term phenotype was proposed by the Danish scientist Wilhelm Johansen in 1909, together with the concept of genotype, to distinguish the heredity of an organism from what results from its implementation. The idea of distinguishing the carriers of heredity from the result of their actions can be traced already in the works of Gregor Mendel (1865) and August Weismann. The latter distinguished (in multicellular organisms) reproductive cells (gametes) from somatic ones.

Factors determining the phenotype

Some characteristics of the phenotype are directly determined by the genotype, such as eye color. Others are highly dependent on the interaction of the organism with the environment - for example, identical twins may differ in height, weight and other basic characteristics. physical characteristics, despite carrying the same genes.

Phenotypic variance

Phenotypic variance (determined by genotypic variance) is a basic prerequisite for natural selection and evolution. The organism as a whole leaves (or does not leave) offspring, so natural selection influences the genetic structure of the population indirectly through the contributions of phenotypes. Without different phenotypes there is no evolution. At the same time, recessive alleles are not always reflected in the characteristics of the phenotype, but are preserved and can be transmitted to offspring.

Phenotype and ontogeny

The factors on which phenotypic diversity, the genetic program (genotype), environmental conditions and the frequency of random changes (mutations) depend are summarized in the following relationship:

genotype + external environment + random changes → phenotype

The ability of a genotype to form different phenotypes in ontogenesis, depending on environmental conditions, is called the reaction norm. It characterizes the share of participation of the environment in the implementation of the characteristic. The wider the reaction norm, the more influence environment and the less the influence of the genotype in ontogenesis. Typically, the more diverse the habitat conditions of a species, the wider its reaction norm.

Examples

Sometimes phenotypes in different conditions are very different from each other. Thus, pine trees in the forest are tall and slender, but in open space they are spreading. The shape of water buttercup leaves depends on whether the leaf is in water or exposed to air. In humans, all clinically detectable characteristics - height, body weight, eye color, hair shape, blood type, etc. are phenotypic.

Literature

What are genotypes?

The term refers to the totality of genes of one organism, which are stored in the chromosomes of each of its cells. The concept of genotype should be distinguished from genome, since both words have different lexical meanings. Thus, the genome represents absolutely all the genes of a given species (human genome, monkey genome, rabbit genome).

How is a person's genotype formed?

What is a genotype in biology? Initially, it was assumed that the set of genes of each cell in the body is different. This idea was refuted from the moment scientists discovered the mechanism of formation of a zygote from two gametes: male and female. Since any living organism is formed from a zygote through numerous divisions, it is not difficult to guess that all subsequent cells will have exactly the same set of genes.

However, it is necessary to distinguish the genotype of the parents from that of the child. The fetus in the womb has half the set of genes from mom and dad, so although children are similar to their parents, at the same time they are not 100% copies of them.

What are genotype and phenotype? What is their difference?

Phenotype is the totality of all external and internal characteristics of an organism. Examples include hair color, presence of freckles, height, blood type, amount of hemoglobin, synthesis or absence of an enzyme.

However, the phenotype is not something definite and constant. If you observe hares, the color of their fur changes depending on the season: in summer they are gray and in winter white.

It is important to understand that the set of genes is always constant, but the phenotype can vary. If we take into account the vital activity of each individual cell of the body, each of them carries exactly the same genotype. However, insulin is synthesized in one, keratin in the other, and actin in the third. Each one is different from each other in shape, size and function. This is called phenotypic manifestation. This is what genotypes are and how they differ from the phenotype.

This phenomenon is explained by the fact that during the differentiation of embryonic cells, some genes are turned on, while others are in “sleep mode”. The latter either remain inactive throughout their lives or are reused by the cell in stressful situations.

Examples of recording genotypes

In practice, the study is carried out using conditional gene encryption. For example, the gene for brown eyes is written capital letter"A", and the manifestation blue eyes- small letter "a". This shows that the trait of brown eyes is dominant, and blue is recessive.

So, based on the characteristics, people can be:

dominant homozygotes (AA, brown-eyed);
heterozygotes (Aa, brown-eyed);
recessive homozygotes (aa, blue-eyed).

Using this principle, the interaction of genes with each other is studied, and usually several pairs of genes are used at once. This raises the question: what is genotype 3 (4/5/6, etc.)?

This phrase means that three pairs of genes are taken at once. The entry will be, for example, like this: АаВВСс. Here new genes appear that are responsible for completely different characteristics (for example, straight hair and curls, the presence of protein or its absence).

Why is the typical genotype notation arbitrary?

Any gene discovered by scientists has a specific name. Most often these are English terms or phrases that can reach considerable lengths. The spelling of names is difficult for representatives of foreign science, so scientists have introduced a simpler recording of genes.

Even a student high school sometimes may know what genotype 3a is. This notation means that a gene is responsible for 3 alleles of the same gene. If the real gene name were used, understanding the principles of heredity might be difficult.

If we're talking about about the laboratories where they are carried out serious research karyotype and the study of DNA, then they resort to official names genes. This is especially true for those scientists who publish the results of their research.

Where are genotypes used?

Another one positive trait Using simple notation is universal. Thousands of genes have their own unique name, but each of them can be represented by just one letter of the Latin alphabet. In the overwhelming majority of cases, when solving genetic problems for various traits, the letters are repeated again and again, and the meaning is deciphered each time. For example, in one problem, gene B is the color of black hair, and in another, it is the presence of a mole.

The question “what are genotypes” is raised not only in biology classes. In fact, the convention of designations causes the vagueness of formulations and terms in science. Roughly speaking, the use of genotypes is a mathematical model. IN real life everything is more complicated, despite the fact that general principle Still managed to transfer it to paper.

By and large, genotypes in the form in which we know them are used in the curriculum of school and university education when solving problems. This simplifies the understanding of the topic “what are genotypes” and develops students’ ability to analyze. In the future, the skill of using such a notation will also be useful, but for real research, real terms and gene names are more appropriate.

The genes are currently being studied in various biological laboratories. Encryption and use of genotypes is relevant for medical consultations when one or more characteristics can be traced over a number of generations. As a result, experts can predict the phenotypic manifestation in children with a certain degree of probability (for example, the appearance of blond hair in 25% of cases or the birth of 5% of children with polydactyly).

The concepts of “genotype” and “phenotype” are intimately related to the concepts of “heredity” and “environment”, but are not identical to them. These concepts were introduced by V. Johannsen in 1909. The concept of “genotype” denotes the sum of all the genes of an organism, the hereditary constitution of the organism, the totality of all hereditary inclinations of a given cell or organism, i.e. a set of genes consisting of deoxyribonucleic acid (DNA) molecules and organized into a chromosomal series. The genotype of an organism will be the result of the fusion of two gametes (an egg and the sperm that fertilizes it). The concept of “phenotype” refers to any manifestations of a living organism - its morphological, physiological, psychological and behavioral characteristics. Phenotypes are not inherited, but are formed throughout life; they are the product of an extremely complex interaction between genotype and environment.

Note that there are single traits whose phenotype is completely determined by their genetic mechanisms. Examples of such characteristics are polydactyly (the presence of an extra finger) or a person’s blood type. At the same time, there are very few such traits, and with very rare exceptions, the phenotype of a trait is determined by the joint influence of the genotype and the environment in which the genotype exists.

For any genotype, there is a range of environments in which it can express itself “maximally”; it is impossible to find an environment equally favorable for all genotypes. The point is not in the “richness” of environments, but in their qualitative diversity. There should be a lot of environments so that each genotype has the opportunity to find “the right” environment and realize itself. It is important to note that a monotonous environment, no matter how enriched it may be, will favor the development of only certain, and not all genotypes.

Reaction norm concept and development

The population approach to assessing the heritability of behavioral traits does not allow us to describe the processes of interaction between the genotype and the environment in individual development. When, as a result of psychogenetic studies conducted, say, on twins or adopted children, a trait is classified as heritable, this does not mean that it is hereditarily determined in the generally accepted sense of the word.

Psychogenetic research is carried out mainly at the population level. When population geneticists draw a conclusion about the heritability of a trait based on correlated behavior among relatives, this does not mean that individual development this behavior due solely to genetic reasons.

High heritability only indicates that the diversity of individuals in a population is largely associated with genotypic differences between them. This means that the percentage of individuals possessing a given trait in a population of offspring can be predicted based on knowledge about the parent population. However, the value of the heritability indicator does not say anything about the sequence of events in the individual development of the trait and what final phenotype will be the result of the development of a particular individual. In this sense, a trait with a high heritability estimate is not a determined genotype, although such interpretations are often found even in the publications of specialists. These are completely different things - to divide the sources of variation in a population into genetic and environmental ones or to look for genetic and environmental reasons that underlie the ontogenetic formation of specific phenotypes.

Even with 100% heritability, as it is understood in behavioral genetics, there is the possibility of environmental influence on the formation of a trait in individual development. This approach corresponds to genetic ideas about the norm of reaction. Let us remember that it is not the trait that is inherited, but the reaction norm.

Special attention should be paid to the reaction norm in this section. In many genetics textbooks, in school biology courses and other books, the reaction norm is often understood as the limits that the genotype places on the formation of the phenotype. This understanding of the reaction norm, in our opinion, is less productive than the one we adhere to in the course of presenting the material. The reaction norm is the specific nature of the genotype’s reaction to environmental changes. The introduction of the concept of limit into the definition of a reaction norm is quite understandable, since under ordinary standard conditions of development, genotypes indeed limit the possibilities for the development of phenotypes. For example, people with good genetic inclinations for the development of intelligence, all other things being equal, will always be ahead of people with poor inclinations. It is believed that the environment can shift the final outcome of development, but within a range that is genetically determined. But, in reality, this is a false premise, since we can never be sure that a trait has reached the maximum development possible for a given genotype.

The pattern of phenotypic manifestations of a genotype cannot be tested for all possible environments because they are uncertain. In relation to humans, we not only do not have the opportunity to arbitrarily control the parameters of the environment in which development occurs, but often, when analyzing environmental influences on a trait, we even find it difficult to select those parameters about which information needs to be obtained, especially when it comes to behavioral characteristics.

Modern developmental psychobiology provides more and more data on the significant capabilities of the environment, in the frequency of early experiences, including embryonic ones, to influence gene activity and structural and functional formation nervous system. Thus, if in a traditional environment the illusion is created that there are limits to the formation of a phenotype, then we cannot be sure that development, during which the genotype will be subjected to unusual, unconventional influences, will not lead to the emergence of such behavioral features that in ordinary conditions under this genotype would be impossible. Thus, it is more correct to think that the limits of the phenotype are unknowable.

Many people follow with interest publications about unconventional methods raising babies, and some parents experience them on their children. Someone is trying to raise a musician, starting from the prenatal period, when the mother carrying the child, with the help of simple devices, provides her fetus with listening musical works or she herself sings lullabies to an unborn child. Some give birth in water and then swim with the newborn in a bathtub or pool. Some people are interested in dynamic gymnastics and conditioning. Increasingly, in maternity hospitals, the baby is not separated from the mother in the first minutes of life, as was traditionally done before, but even before the umbilical cord is cut, they are placed on her stomach, ensuring such natural contact between the mother and the newborn.

All these “experiments” are nothing more than the influence of non-traditional (for a given period of development of society) early experience on the fetus and newborn, and these influences are not meaningless, since the intensively developing nervous system, on which, ultimately, will depend our behavior and all higher mental functions are very susceptible to influence precisely in early period ontogeny. What is known today about the influence of early experience, that is, the environment, on the development of the nervous system and can this environment directly influence the functioning of the genetic apparatus? In other words, this is a question of what knowledge we have about the process of interaction between genotype and environment in individual development.

How can environment interact with genotype during development?

It is clear that the result of development - the phenotype - depends on the joint action of genes and the environment. Genes and traits are linked through a complex network of developmental pathways. All individual differences that differential psychologists and psychogeneticists are concerned with are the result of the developmental circumstances of specific individuals in specific environments. Often individuals brought up in apparently different environments have much in common. Conversely, siblings raised in the same family, seemingly under similar circumstances, due to subtle differences in the conditions of upbringing and development, will actually experience very different influences from both the physical and social environment.

Thus, the process of interaction with the environment is complex and ambiguous. Note also that psychologists and other researchers often use the term “interaction” in a statistical sense when examining the interaction of individual factors in the production of any measurable effect. We emphasize that the statistical interaction of factors and the interaction of genes and environment in individual development are completely different things. They should not be confused.

For us, the formulation is quite familiar, which states that the manifestation of a phenotype is the result of the interaction of the genotype with the environment during development. However, if you think about this statement, it does not seem so obvious. After all, interaction presupposes that its participants come into contact and come into contact. In fact, our genotype, that is, the genetic apparatus, is hidden deep inside the cell and is separated from the external environment not only by the integument of the body, but also by the cellular and nuclear membranes. How can the external environment interact with genetic structures?

It is clear that genes and the world are not in direct contact. The organism as a whole interacts with the external environment; genes interact with various biochemical substances inside the cell. But various cellular substances can be influenced outside world. Let's consider what is known about these processes today's science. To do this, we will again have to turn to molecular genetics and consider in more detail how genes function, since in the previous presentation we only stated that main function A gene is the encoding of information necessary for the synthesis of a specific protein.

Accidents of development

The variability of developmental phenomena depends on many reasons. Heredity tends to reduce developmental variability, whereas conditions not associated with heredity tend to increase it. Some developmental researchers identify four types of random factors that influence developmental variability:

accidents in the selection of parental pairs, the genes of which make up the genotype of the individual;
randomness of epigenetic (that is, external to the genotype) processes within individual ontogenesis;
the randomness of the maternal environment in which the individual develops;
the randomness of the non-maternal environment in which the individual develops.

Although these are random events, they all have an element of heredity. The genotype is inherited from the parents, and the offspring and parents have common genes that influence the course of individual development. Epigenetic processes within the body represent the influence of other cells or their products on the activity of the genotype of a given cell. Since all cells in the body have the same genotype, it is natural that epigenetic influences are associated with heredity. However, epigenetic processes are stochastic, open to the influence of environmental factors of the organism and, therefore, to any historical accidents.

The maternal environment of mammals is very important element external environment. Mothers provide the intrauterine and postnatal (baby care and education) environment for the child. It is clear that these conditions are influenced by the mother's genotype. Partially, the mother's genes are shared with the offspring, so the maternal environment can be inherited. The maternal environment is also sensitive to historical contingencies.

Nonmaternal environmental effects also influence developmental variability. This includes factors that are chosen by the individual himself or shaped by the people around him, including relatives with whom he shares genes. Therefore, these environmental effects, to some extent, are also influenced not only by random environmental events, but also by genes, and are also inherited (genotype-environmental covariation).

Thus, in accordance with the above classification, in all the described elements of the environment external to a given individual there are mechanisms for inheritance, both genetic and non-genetic ( different traditions and so on.).

Naturally, non-heritable factors also influence development. These are those features of the environment that are not associated with changes caused by the developing individual himself or his related environment. They can be either random or natural. Regular changes include cyclical changes (change of day and night, change of seasons, etc.), widespread influences (gravity) or predictable factors (temperature, pressure). Non-heritable factors are also present in maternal and other social environment(quality of mother’s nutrition, mother’s stress level, number and gender of siblings, etc.). Randomly or systematically changing environmental events contribute to variability in development.

All events external to genes that take place during the process of ontogenesis, together with genetic factors, create the background against which development takes place. Due to the influence of a huge variety of natural and random events During ontogenesis, developing systems can organize and reorganize. Genes make development possible, but other components that influence the development of the system are no less important participants in the development process.

At the beginning of the presentation, defining the concept of phenotype, we emphasized that the phenotype is the result of the interaction of the genotype and the environment, however, in the light of what has been said about the process of individual development, we must make some clarification in this formulation and, along with environmental factors, mention accidents of development that cannot be reduced to purely environmental influences. If we tried to graphically depict the dependence of the phenotype on various factors, then we would need at least a four-dimensional space in which, in addition to the axes for genotype and environment, there would also have to be an axis for the accidents of development.

Endophenotype as an intermediate level between genotype and phenotype

The wide range of CIs of different abilities makes it necessary to address the intermediate level between genotype and phenotype. If the genotype is the sum of all the genes of an organism, then the phenotype is any manifestations of a living organism, “the product of the implementation of a given genotype in a given environment.” There is no direct correspondence between the gene (genotype) and behavior (phenotype), but only a repeatedly mediated connection. Phenotypically identical traits measured using the same methodology may have different psychological structures depending on the age and individual characteristics of the individual and, accordingly, may be associated with different genes. The presence, absence, and degree of expression of one phenotypic trait are determined by many genes, the result of which depends not only on the available gene variants, but also on many other factors. “Direct biochemical manifestation of a gene and its influence on psychological characteristics separated by a “mountain range” of intervening biomolecular events.” Therefore, one of the ways to facilitate tracing the path from genes to behavior is to find endophenotypes—intermediate links that mediate the influence of the genotype on phenotypic variables.

The concept of endophenotype, introduced by I. Gottesman in 1972 when studying mental disorders, received wide use and in the analysis of psychological and psychophysiological characteristics.

A trait or indicator can be recognized as an endophenotype of cognitive abilities if it meets the following criteria:

it is stable and reliably determined;
its genetic condition was revealed;
it correlates with the cognitive ability being studied (phenotypic correlation);
the relationship between it and cognitive ability is partly inferred from common genetic sources (genetic correlation). And if the task is to trace the biological path from genes to cognitive ability, then it is important to fulfill one more criterion;
the presence of a theoretically meaningful (including causal) relationship between the indicator and cognitive ability.

It is customary to consider private cognitive characteristics or individual characteristics of the functioning of the brain, its anatomy and physiology as endophenotypes of intelligence.

Among the private cognitive characteristics, the reaction time of choice is used. It is known that individual differences in choice reaction time explain about 20% of the variance in intelligence scores. It was found that the associations between choice reaction time and verbal and non-verbal intelligence scores were explained by genetic factors: 22 and 10% of common genes were found, respectively. It is assumed that among the common genes there are those responsible for the myelination of CNS axons (as is known, an axon covered with a myelin sheath conducts a nerve impulse faster). Particular cognitive characteristics considered as endophenotypes of intelligence include working memory. However, we note that neither choice reaction time, nor working memory, nor other psychological parameters important for understanding the nature of intellectual differences, still do not reveal the path from genotype to intelligence through the structure and functioning of the brain, since they are not direct indicators of brain function. In addition, when using these indicators, we again encounter the above-mentioned high sensitivity of the CI to changes in experimental conditions.

Parameters of brain functioning on the brain are also considered possible endophenotypes. different levels physiology, morphology and biochemistry of the brain, including structural proteins, enzymes, hormones, metabolites, etc. The EEG, the speed of nerve impulses, the degree of myelination of nerve fibers, etc. are examined. It has been shown that peripheral nerve conduction velocity (PNCV) and brain size correlate with intelligence. Amplitude-temporal and topographic characteristics of evoked potentials were studied as intermediate phenotypes of intelligence. However theoretical justifications The connections between these characteristics and intelligence, as a rule, do not reveal the specifics of intellectual abilities. Thus, brain size is correlated with the thickness of the myelin sheath, which may be less or better at protecting cells from the influence of neighboring neurons, which is said to influence intelligence. SPNP determines the quantitative characteristics of protein transmission, and its limitation leads to a limitation in the speed of information processing, which leads to a decrease in intelligence indicators.

A connection has been established between the general intelligence factor (g factor) and the amount of gray matter. Another possible endophenotype of cognitive abilities is the specific arrangement of brain structures. It is revealed that the CI of the structural characteristics of the brain is very high, especially in the frontal, associative and traditional speech zones (Wernicke and Broca). Thus, in the area of the median frontal structures, we can reliably speak of a CI of the order of 0.90–0.95.

However, endophenotypes that directly reflect the morphofunctional characteristics of the brain do not take into account the ability to plan activities, the strategies used and other features that significantly affect the success and speed of problem solving, i.e. do not take into account the psychological organization of the phenotype under study (cognitive abilities). There is an indirect connection between endophenotypes of this kind and intelligence: endophenotypes reflect a level of analysis that is far from intelligence and therefore do not provide a holistic picture of the path to the formation of intellectual functions.

E. De Geus and co-authors consider it very productive to use neurophysiological characteristics and the results of direct measurements of brain structures and their functioning using EEG, MRI, etc. as endophenotypes (in addition to special cognitive abilities).

However, the use of neurophysiological indicators in studies on behavioral genetics leads to the need to adapt neuroscience methods to the requirements of psychogenetics. The problem is that, as R. Plomin and S. Kosslin write, neuroscience is primarily interested in general patterns, as a result of which data are usually averaged and only average values are analyzed. Psychogenetics, on the contrary, is interested in the scatter of individual indicators, which in a number of neuroscience methods reflects not only individual characteristics, but also the insufficient accuracy of the equipment. This creates significant difficulties in obtaining reliable data. In addition, the technical complexity of these methods does not allow the study of large enough samples necessary for psychogenetic analysis.

conclusions

Developmental research in psychogenetics is conducted at the population level; the resulting quantitative relationships between the genetic and environmental components of variability are not applicable to the development of a specific phenotype. It must be remembered that the mutual influences of genotype and environment in individual development are inseparable.
The formation of a phenotype in development occurs through continuous interaction between the genotype and the environment. Environmental factors (physical, social) can influence the genotype through factors of the internal environment of the body (various biochemical substances inside the cell).
The main mechanism of interaction between genotype and environment at the cellular level is the regulation of gene expression, manifested in different activity of specific protein synthesis. Most of the regulatory processes occur at the transcription level, that is, they concern the processes of reading genetic information necessary for protein synthesis.
Among all the organs of the body, the brain ranks first in the number of active genes. According to some estimates, almost every second gene in the human genome is associated with the functions of the nervous system.
Early experience has significant opportunities to influence the functioning of the genetic apparatus. A special role here belongs to the so-called early genes, which are capable of rapid but transient expression in response to signals from the external environment. Apparently, early genes play a significant role in learning processes. Significant possibilities for regulating gene expression are also associated with the action of various hormones.
The development of the nervous system and, ultimately, behavior is a dynamic, hierarchically organized systemic process in which genetic and environmental factors are equally important. An important role is also played by various accidents of development, which cannot be reduced to purely environmental factors.
Development is an epigenetic process that results in significant interindividual variability, even in isogenic organisms. The basic principle of the morphogenesis of the nervous system is the occurrence of maximum redundancy of cellular elements and their connections in the early stages of development, followed by the elimination of functionally unstable elements in the process of reciprocal interaction between all levels of the developing system, including interactions within the cell, between cells and tissues, between the organism and the environment.
The process of phenotype formation in development is of a continuous dialectical and historical nature. At any stage of ontogenesis, the nature of the body’s response to environmental influences is determined both by the genotype and the history of all developmental circumstances.