The interaction of several non-allelic genes, leading to the development of a new trait that is absent in parents, is called complementarity. Non-allelic genes in this case complement each other, as a result of which a completely different trait develops.
Complementarity is widespread in nature. The result of this interaction of non-allelic genes is the inheritance of hair color in mice, color of flowers in sweet peas, and the shape of fruits in pumpkins. Epistatic. the interaction is associated with the synthesis of regulatory proteins. In one case, a regulatory gene synthesizes a protein that suppresses the transcription of the main structural gene responsible for the development of a trait. In another case, the regulatory gene, on the contrary, is not able to synthesize a protein that regulates the activity of the structural gene. In either case, the trait does not develop, since the protein responsible for the trait is not synthesized.
An example of epistasis in humans is the “bombing phenomenon” in the inheritance of blood groups. It is described in a woman who received the IB allele from her mother, but phenotypically having the first blood group. It turned out that the activity of the IB allele is suppressed by a rare recessive allele of gene x, which in the homozygous state exerts an epistatic effect. Polymeria (from the Greek. Polymeria – polysyllabic). With this interaction, the intensity of the manifestation of the trait is due to several pairs of equivalent genes (they are called polymer genes): the more identical alleles are, the more intense the trait is. An example of a polymer is the inheritance of skin color in humans, which depends (in a first approximation) on four genes with a cumulative effect.
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