What is a phenotype? Concept, main characteristics, interaction with genotype. Phenotype: definition, examples, relationship with genotype and genetic diversity

The genotype is the totality of all the genes of an organism, which are its hereditary basis.

Phenotype is the totality of all the signs and properties of an organism that are revealed in the process of individual development in given conditions and are the result of the interaction of the genotype with a complex of factors internal and external environment.

Phenotype in general is what can be seen (a cat's color), heard, felt (smelled), and the behavior of the animal. Let's agree that we will consider the phenotype only from the point of view of color.

As for the genotype, they most often talk about it, meaning a certain small group of genes. For now, let's assume that our genotype consists of just one gene W(in the following paragraphs we will sequentially add other genes to it).

In a homozygous animal, the genotype coincides with the phenotype, but in a heterozygous animal, it does not.

Indeed, in the case of genotype WW, both alleles are responsible for white color, and the cat will be white. Likewise ww- both alleles are responsible for non-white color, and the cat will not be white.

But in the case of genotype Ww the cat will be externally (phenotypically) white, but in its genotype it will carry a recessive allele of a non-white color w .

Every biological species has a phenotype unique to it. It is formed in accordance with the hereditary information contained in the genes. However, depending on changes in the external environment, the state of traits varies from organism to organism, resulting in individual differences - variability.

Based on the variability of organisms, genetic diversity of forms appears. A distinction is made between modificational, or phenotypic, and genetic, or mutational variability.

Modifying variability does not cause changes in the genotype; it is associated with the reaction of a given, one and the same genotype to changes in the external environment: under optimal conditions, the maximum capabilities inherent in a given genotype are revealed. Modification variability manifests itself in quantitative and qualitative deviations from the original norm, which are not inherited, but are only adaptive in nature, for example, increased pigmentation of human skin under the influence of ultraviolet rays or development of the muscular system under the influence of physical exercise, etc.

The degree of variation of a trait in an organism, that is, the limits of modification variability, is called the reaction norm. Thus, the phenotype is formed as a result of the interaction of the genotype and environmental factors. Phenotypic characteristics are not transmitted from parents to offspring, only the reaction norm is inherited, that is, the nature of the response to changes in environmental conditions.
Genetic variability can be combinative and mutational.

Combinative variability arises as a result of the exchange of homologous regions of homologous chromosomes during the process of meiosis, which leads to the formation of new gene associations in the genotype. Occurs as a result of three processes:

1) independent chromosome segregation during meiosis;
2) their accidental combination during fertilization;
3) exchange of sections of homologous chromosomes or conjugation.

Mutational variability. Mutations are abrupt and stable changes in units of heredity - genes, entailing changes in hereditary characteristics. They necessarily cause changes in the genotype, which are inherited by the offspring and are not associated with crossing and recombination of genes.
There are chromosomal and gene mutations. Chromosomal mutations are associated with changes in the structure of chromosomes. This may be a change in the number of chromosomes that is a multiple or not a multiple of the haploid set (in plants - polyploidy, in humans - heteroploidy). An example of heteroploidy in humans can be Down syndrome (one extra chromosome and 47 chromosomes in the karyotype), Shereshevsky-Turner syndrome (one X chromosome is missing, 45). Such deviations in a person’s karyotype are accompanied by health disorders, mental and physical disorders, decreased vitality, etc.

Gene mutations affect the structure of the gene itself and entail changes in the properties of the body (hemophilia, color blindness, albinism, etc.). Gene mutations occur in both somatic and germ cells.
Mutations that occur in germ cells are inherited. They are called generative mutations. Changes in somatic cells cause somatic mutations that spread to that part of the body that develops from the changed cell. For species that reproduce sexually, they are not significant, for vegetative propagation plants they are important.

What is Genotype and Phenotype

Genotype is kit genetic information, which is responsible for the structure of the body and gives it inherited traits. In other words, we can say that a genotype is the genetic code of an organism, which exists in the form of genetic data such as DNA or RNA. Phenotype is an external physical manifestation of an organism that can be observed visually without resorting to studies of the genetic code.

What is GENOTYPE and PHENOTYPE - definition in simple words.

In simple words, Genotype is internal encoded heritable information that is carried by all living beings. It's kind of general plan or a set of instructions for building a new organism, which specifies all the parameters of how the given organism should look and function. These instructions are transmitted in encoded form - genetic code. In turn, the genetic code is present in all cells of the body, and it is copied during cell division or reproduction, passing on hereditary information to offspring. The information contained in the genetic code is directly related to all aspects of the life of the cell and the organism as a whole. It is she who controls absolutely all processes, from the formation of protein macromolecules to the regulation of metabolism and.

In simple words, Phenotype is the appearance and behavior of a particular individual. In other words, this is the result of what the organism has become under the influence of the components of the genotype, the ratio of dominant alleles and environment.

GENOTYPE and PHENOTYPE - how they differ.

Speaking of such two concepts as “genotype” and “phenotype”, first of all it should be noted that they are indeed closely related to each other, but have fundamental differences. The fact is that the term Genotype is applicable specifically to the genetic information contained in the gene code. The genotype can only be determined through biological tests and studies. In turn, the phenotype is the consequences of the genotype and other factors that can simply be seen.

If we talk about the differences quite simply, then:

• Genotype is a code (you can't just see him);
• Phenotype is the way the code manifests itself (you can observe: eye color, hair, height, behavior, etc.).

There are two very important concepts in genetics. 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. Phenotype includes both 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 they are not inherited - they develop and are a consequence of our genotypes only to a certain extent, since environmental conditions play a large role in the formation of phenotypes.

The entire development process 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 various conditions the environment in which the growing organism is located. Therefore, the extraordinary variability characteristic of living organisms is due not only to the enormous diversity of genotypes arising as a result of gene recombination and the mutation process, but is also largely due to the fact that 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 where it concerns 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 to put two concepts side by side in a scientific treatise, which in one form or another have not left the pages of scientific literature to this 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.

Genotype and phenotype are concepts that schoolchildren are introduced to in high school in the course “ General biology" Due to the similarity of sound, potential graduates very often confuse two basic biological terms.

Genotype- this is the set of genes that a living organism received at birth. In other words, this is - full set genetic information possessed by a particular biological individual. The jurisdiction of the term includes not only groups of genes or alleles, but also types of linkages between each other in the chromosome of these carriers hereditary information.

The set and combination of genes directly affects development, internal and external structure, features of the life processes of a particular organism. To determine the genotype, genetic analysis or examination should be performed. In crop production and livestock breeding, analytical crossbreeding is used to isolate the desired gene.

The same genotype is recorded in identical twins. For example, two living beings - a kitten, a child, a mouse of the same sex, which were formed from one fertilized egg. If a biological species reproduces by vegetative means (division, reproduction by spores, budding) or the number of organisms increases due to cloning, then until a mutation occurs, individuals have a similar genetic makeup.

The term was coined by Mr. Johansen in 1909 when he published the results of a study of heredity. A significant part of the genes present in the body are manifested in the phenotype of the organism.

Phenotype- these are the internal and external parameters of the body that appeared in it as a result of ontogenesis, that is, during its individual development. The phenotype is based on the genotype - a set of genes, possible mutations and environmental factors. For example – temperature, radiation level, salt concentration in water. In organisms with a diploid or double set of chromosomes, only dominant genes appear in the phenotype. Recessive alleles most often do not appear in the phenotype, but they are preserved in the genotype and can be inherited by the body.

The higher the level of organization of the organism and its sensitivity to external factors, the more opportunities there are for phenotypic variations.

The term phenotype was coined by the above-mentioned Dane Johansen simultaneously with the concept of “genotype” to distinguish between specific heredity and how a specific organism implemented its genetic program.

An ideal example to demonstrate the capabilities of a phenotype would be a story about two identical twins who have the same gene set a priori. By placing them on initial stage development in different living conditions - climatic, social, you will get organisms that are very different in a number of external and quality of internal parameters. But we should not forget that there are traits that are determined only by the genotype. For example, eye color or blood type.

Conclusions website

1. A living organism receives its genotype from its parents as a result of the merger of two carriers of hereditary information. The phenotype is formed on the basis of the genotype, it is influenced by a number of external factors and inevitable mutations.
2. The genotype can be determined after DNA analysis, the phenotype can be seen with the naked eye, already when analyzing the parameters appearance living organism.
3. An individual passes on a set of genes to his offspring; the phenotype is formed in the process of individual development of a living being.

This is what “parsley” looks like, to say the least. Once again I am faced with the fact that the fundamental concepts of genetics are presented in textbooks in such a way that it can be difficult to understand them.

I was tempted to call this article that way at first "Phenotype and genotype." It is clear that the phenotype is secondary to the genotype. But if students can most often interpret the term “genotype” correctly, then as it turns out, there is no clear idea regarding the concept of “phenotype”.

How can it be “clear” if the definitions of phenotype in educational literature are so vague.

"Phenotype- the totality of all external signs organism, determined by genotype and environmental conditions.” Or “Phenotype is the totality of all external and internal characteristics and properties of an organism, depending on the genotype and environmental conditions.”

And if there really are both “external” and “internal”, and this is actually the case, then what is the difference between a phenotype and a genotype?

Still, you have to start not from the “tail”, but from the “head”. I am sure that a couple of minutes will pass and you, having somewhat clarified for yourself what the “genotype of an organism” is, will be able to get a clearer idea of ​​the “phenotype”.

We often use the terms “trait” and “gene” as synonyms.

They say that “a genotype is the totality of all the characteristics of an organism.” And here it is important to understand the most important thing - it is precisely in the determination of the genotype that such a definition introduces additional confusion. Yes, indeed, information about any trait is encoded in any gene (or set of genes) of the organism.

But there are a lot of genes, the entire genotype of an organism is huge, and during the life of a given individual or individual cell, only a small part of the genotype is realized (that is, serves to form any specific characteristics).

Therefore, it would be correct to remember that "genotype- the totality of all genes organism." And which of these genes are realized during the life of the organism in its phenotype, that is, will serve the formation of any signs- this depends both on the interaction of many of these genes and on specific environmental conditions.

Thus, if we correctly understand what a genotype is, then there is no loophole for confusion in terms of what is a “genotype” and what is a “phenotype”.

It is clear that “a phenotype is the totality of all genes realized during the life of an organism that contributed to the formation of specific characteristics of a given organism under certain environmental conditions.”

Therefore, throughout the life of an organism, under the influence of changing environmental conditions, the phenotype can change, although it is based on the same unchanged genotype. And within what limits can the phenotype change?

Reaction rate

These boundaries for the phenotype are clearly delineated by the genotype and are called “reaction norms.” After all, nothing can appear in the phenotype that was not already “recorded” earlier in the genotype.

To better understand what is included in the concept of “reaction norms”, let’s look at specific examples possible manifestation of a “broad” or “narrow” reaction norm.

The weight (mass) of the cow and the milk yield of the cow, which trait has a wider and which has a narrower reaction rate?

It is clear that the weight of an adult cow of a certain breed, no matter how well it is fed, cannot exceed, for example, 900 kg, and if it is poorly maintained, it cannot be less than 600 kg.

What about milk yield? With optimal maintenance and feeding, milk yield can vary from some maximum possible value for a given breed, it can drop to 0, with unfavorable conditions content. This means that the mass of a cow has a rather narrow reaction rate, and the milk yield is very wide.

Example with potatoes. It is obvious to anyone that the “tops” have a rather narrow reaction rate, and the mass of tubers has a very wide one.

I think everything has settled down now. The genotype is the set of all the genes of an organism, this is its entire potential of what it can be capable of in life. And the phenotype is only a manifestation of a small part of this potential, the implementation of only part of the organism’s genes into a number of specific characteristics during its life.

A clear example of the transformation of part of its genotype into a phenotype during the life of an organism are identical twins. Having absolutely the same genotype, in the first years of life they are almost indistinguishable from each other phenotypically. But as they grow up, having at first minor differences in behavior, in some attachments, giving preference to one or another type of activity, these twins become quite distinguishable phenotypically: in facial expression, body structure.

At the end of this note, I would like to draw your attention to something else. The word genotype for students of the basics of genetics has two meanings. Above we examined the meaning of “genotype” in its broad sense.

But to understand the laws of genetics, when solving genetic problems, the word genotype means only a combination of some specific individual alleles of one ( monohybrid cross) or two (dihybrid crossing) pairs of certain genes that control the manifestation of a specific one or two traits.

That is, our phenotype is somehow truncated, we say “the phenotype of an organism,” but we ourselves have studied the mechanism of inheritance of only one or two of its characteristics. In a broad sense, the term “phenotype” refers to any morphological, biochemical, physiological and behavioral characteristics of organisms.

P.S. In connection with the characteristics of the concepts “genotype” and “phenotype,” it would be appropriate here to examine the question of hereditary and non-hereditary forms of variability in organisms. Well, okay, that’s exactly what we’ll talk about in.

***************************************************************

Who has questions about the article to Biology tutor via Skype, comments, wishes - please write comments.