Genetics has repeatedly amazed us with its achievements in the study of the human genome and other living organisms. The simplest manipulations and calculations cannot do without generally accepted concepts and signs, which this science is not deprived of.
What are genotypes?
The term is understood as 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 the genome, since both words have a different lexical meaning. Thus, the genome represents absolutely all the genes of a given species (human genome, monkey genome, rabbit genome).
How is the human genotype formed?
What is a genotype in biology? Initially, it was assumed that the set of genes of each cell of the body is different. Such an idea has been refuted since the moment scientists discovered the mechanism for the formation of a zygote from two gametes: male and female. Since any living organism is formed from a zygote through numerous divisions, it is easy to guess that all subsequent cells will have exactly the same set of genes.
However, the genotype of the parents should be distinguished from that of the child. The fetus in the womb has half the set of genes from mom and dad, so children although they look like their parents, but at the same time they are not 100% copies of them.
What is genotype and phenotype? How are they different?
Phenotype is a combination of all external and internal signs of an organism. Examples are hair color, freckles, height, blood type, hemoglobin count, enzyme synthesis or absence.
However, the phenotype is not something definite and permanent. If you watch the hares, the color of their coat changes depending on the season: they are gray in summer and white in winter.
It is important to understand that the set of genes is always constant, and the phenotype can vary. If we take into account the vital activity of each individual cell of the body, any of them carries exactly the same genotype. However, insulin is synthesized in one, keratin in the other, and actin in the third. Each is not similar to each other in shape and size, functions. This is called phenotypic expression. Here 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 included in the work, while others are in “sleep mode”. The latter either remain inactive all their lives, or are reused by the cell in stressful situations.
Examples of recording genotypes
In practice, the study of hereditary information is carried out using conditional encoding of genes. For example, the gene for brown eyes is written with a capital letter "A", and the manifestation of blue eyes is written with a small letter "a". So they show that the sign of brown-eyedness is dominant, and the blue color is recessive.
So, on the basis of people can be:
- dominant homozygotes (AA, brown-eyed);
- heterozygotes (Aa, brown-eyed);
- recessive homozygotes (aa, blue-eyed).
This principle is used to study the interaction of genes with each other, and usually several pairs of genes are used at once. This begs 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, this: AaVVSs. New genes appear here that are responsible for completely different traits (for example, straight hair and curls, the presence of protein or its absence).
Why is the typical genotype notation conditional?
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 record of genes.
Even a high school student can sometimes know what genotype 3a is. Such a record means that 3 alleles of the same gene are responsible for the gene. Using the actual name of the gene would make it difficult to understand the principles of heredity.
When it comes to laboratories where serious karyotype and DNA studies are carried out, then they resort to the official names of genes. This is especially true for those scientists who publishthe results of their research.
Where genotypes apply
Another good thing about using simple notation is its versatility. Thousands of genes have their own unique name, but each of them can be represented by only one letter of the Latin alphabet. In the overwhelming majority of cases, when solving genetic problems for different signs, the letters are repeated again and again, and each time the meaning is deciphered. For example, in one task gene B is 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 conventionality of designations causes the fuzziness 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 the general principle still managed to be transferred to paper.
By and large, genotypes in the form in which we know them are used in the program of school and university education in 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 in real research, real terms and gene names are more appropriate.
Currently, genes are being studied in various biological laboratories. Encryption and use of genotypes is relevant for medical consultations when one or more traits can be traced ina 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 blondes in 25% of cases or the birth of 5% of children with polydactyly).
