Interaction of genes
A gene is a structural unit of inherited information. It is a specific part of the DNA molecule( sometimes RNA).The interaction of genes ensures the transfer of elementary signs of parental organisms to offspring.
Each gene defines a specific feature that does not depend on others. They are able to interact. This is possible due to the fact that linked gene inheritance occurs. When combined into a genotype, they act as a system. The main relations between them are dominance and recessivity.
The human genotype is thousands of characters( system) that fit in only 46 chromosomes. Each of them contains a huge number of genes( not less than 30 thousand).
The degree of development of a specific trait may be due to the influence of not one gene, but a whole series, which are interconnected in a free manner. This interaction of genes is commonly called a polymer( multisyllabic).By this mechanism, the skin color, hair and hundreds of other traits are inherited.
Thanks to this number of genes, life activity and development of definitive organisms are provided, consisting of various types of specialized differentiated cells. In humans, about 200 cell types have been identified, with additional subdivisions into a number of more specialized functional and morphological types of cells.
The combination of genes in one chromosome is determined by the term "gene linkage".All genes belonging to the same clutch group are inherited together when gametes are formed.
In different clutch groups, the number of genes is not the same. Dihybrid interaction is characterized by the fact that such a linkage does not obey the laws of Mendel. However, full adhesion is rare. As a rule, all four phenotypes are represented in the offspring.
Isolate the allelic and non-allelic interaction of genes. Alleles are forms of the same gene.
Allelic - the interaction of the genes entering into one allelic pair. The manifestation of the sign is determined not only by the relationship of dominance, but also by the number of genes in the genotype.
Allelic genes are capable of creating such connections as complete dominance( when the phenotype of heterozygotes is the product of only one gene) and incomplete( the heterozygote phenotype differs from the homozygote phenotype by the dominant trait and the recessive one, taking the mean( intermediate) value with respect to them.) Co-such interaction of allelic genes when heterozygotes in the phenotype have a product of both
Non-allelic is the joint effect of two( several) non-allelic genes. It can be expressed in the form of an epistatic,polymeric or modifying interaction
The interaction of non-allelic genes can take place in different ways, therefore several types are distinguished:
Complementary - the interaction of genes independently mutating in one genotype and causing the appearance of any one characteristic
Polymer is an additive effect of a number of non-allelicgenes on the formation of a certain feature, which causes a variational continuous series in quantitative terms. Polymeria is cumulative and non-cumulative. In the first case, the manifestation of the trait is determined by the number of dominant alleles of polymer genes that are contained in the genotype. In the second case, the degree of development of the trait is determined only by the presence of dominant alleles and does not depend on their number.
Epistatic - suppression of one gene by the dominant allele of another, non-allelic first. Or suppression of the action of the dominant and recessive allele in the hypostatic gene by the recessive allele of the epistatic allele in the homozygous state.
Complementary - the symptom develops with the mutual action of 2 dominant genes, which individually do not cause development of the trait.
Modifying - a change in the action of the main genes with non-allelic modifiers. One gene can act as the main one in controlling the development of a trait and modifier in relation to the development of another trait.
Interaction of genes is always observed when several genes affect the formation of a certain state of any sign of the organism.