Why most of the mutations do not appear externally?

Natural populations are saturated with a wide variety of mutations. The Russian scientist Sergey Sergeyevich Chetverikov (1880–1959) drew attention to this, who established that a significant part of the gene pool variability is hidden from the eyes, since the vast majority of emerging mutations are recessive and do not appear externally. Recessive mutations seem to be “absorbed by the species in a heterozygous state,” because most organisms are heterozygous for many genes. Such latent variability can be detected in experiments with the crossing of closely related individuals. With this crossing, some recessive alleles that were in a heterozygous and therefore latent state will go into a homozygous state and can manifest themselves. Significant genetic variability of natural populations is easily detected during artificial selection. In case of artificial selection from the population, those individuals are selected for which any economically valuable traits are most strongly expressed, and these individuals are interbred. Artificial selection is effective in almost all cases when they resort to it. Consequently, in populations there is genetic variation literally for every trait of a given organism.

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