Genetics has repeatedly struck 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 understand 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 carry different lexical meanings. So, the genome is absolutely all the genes of a given species (human genome, monkey genome, rabbit genome).
How is a human 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 disproved from the moment scientists discovered the mechanism of zygote formation from two gametes: male and female. Since any living organism is formed from the zygote by 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 embryo in the womb has half the set of genes from mom and dad, so the children, although similar to their parents, are at the same time not their 100% copies.
What is a genotype and phenotype? What is their difference?
A phenotype is a combination of all external and internal signs of an organism. Examples include hair color, the presence of freckles, growth, blood type, amount of hemoglobin, synthesis or lack of an enzyme.
However, the phenotype is not something definite and permanent. If you watch the hares, then the color of their hair varies 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, and the phenotype can vary. If we take into account the vital activity of each individual cell of the body, any of them carries the exact 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 a 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 included in the work, while others are in “sleep mode”. The latter either remain inactive throughout their lives, or are reused by the cell in stressful situations.
Genotype Recording Examples
In practice, the study of hereditary information is carried out using conditional gene encryption. For example, the brown eye gene is written in the capital letter “A”, and the manifestation of blue eyes in the small letter “a”. So they show that the sign of brown eyes is dominant, and the blue color is a recessive.
So, on the basis of people can be:
- dominant homozygotes (AA, brown-eyed);
- heterozygotes (Aa, brown-eyed);
- recessive homozygotes (aa, blue-eyed).
According to this principle, the interaction of genes with each other is studied, and usually several pairs of genes are used at once. This begs the question: what is the 3rd genotype (4/5/6, etc.)?
This phrase means that three pairs of genes are taken at once. The record will be, for example, such: 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 a typical genotype notation conditional?
Any gene discovered by scientists has a specific name. Most often, these are English terms or phrases, which in length can reach considerable dimensions. 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. When using the real name of a gene, understanding the principles of heredity might be difficult.
If we are talking about laboratories where serious studies of the karyotype and DNA are carried out, then they resort to the official names of the genes. This is especially true for those scientists who publish the results of their research.
Where genotypes are used
Another positive feature of using simple notation is its versatility. 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 vast majority of cases, when solving genetic problems for different characters, the letters are repeated again and again, with each meaning being deciphered. For example, in one task, gene B is the black color of the hair, and in another, the presence of a mole.
The question “what are genotypes” is raised not only in biology classes. In fact, the conventions of notation determine 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 school and university curriculum in solving problems. This simplifies understanding of the topic “what are genotypes” and develops students' ability to analyze. In the future, the skill of using such a record will also be useful, however, in real research, these terms and gene names are more appropriate.
Genes are currently being studied in various biological laboratories. Encryption and use of genotypes is relevant for medical consultations, when one or more characters are traced in a number of generations. At the exit, specialists can predict the phenotypic manifestation in children with a certain degree of probability (for example, the appearance in 25% of cases of blondes or the birth of 5% of children with polydactyly).