The study of the realization of hereditary variability on the background of already existing mutant alleles of certain genes is an important part of biomedical and population investigations, including human diseases. The change in viability parameters in individuals of the wild type Belgorod and in the mutant strain of vestigial Drosophila melanogaster over the course of breeding has been researched. The changes in viability parameters during breeding have been recorded in hybrid individuals heterozygous for vestigial, namely, changes in fertility and embryonic lethality of offspring in hybrid individuals Belgorod × vestigial during direct selection, the presence of regulated cell death in the wing imaginal disc in individuals of the Belgorod and vestigial strains, and in hybrid individuals at the initial stage of breeding and after 30 generations of selection. The wing shape changes in interlinear hybrid individuals at different stages of breeding in relation to wild-type individuals Belgorod have been studied. The research methods are the following: selection, study of the frequency of death of offspring at the embryonic stage of development, fertility study, morphometric analysis of the wing, determination of the presence and location of regulated cell death in the wing imaginal disk, statistical analysis. The marker parameters of the wing sensitive to the presence of the mutant allele vg in the genotype, not associated with change in the intensity of regulated cell death in the wing imaginal disc have been revealed.