[Directed character of genetic variation during long-term selection of Drosophila melanogaster strains for adaptively important characters].

Related fly strains that were selected for differences in reproductive function for about 700 generations were studied. The low-active (LA) strain differs from other related and highly active strains of interest at a set of characters. Qualitative differences in the spectrum of viability mutations are retained in strains selected in opposite directions. Low-active strains carry a great number of deleterious mutations. Such mutations are rare in the related highly active strains. Moreover, about 50% of chromosomes in the highly active strains carry supervital mutations, which increase viability. Recombination analysis showed the presence of at least several viability mutations in each chromosome of the strains studied. Unlike highly active strains, the low-active ones are characterized by an extremely high spontaneous mutation rate. The conservation of genetic heterogeneity observed in long-term selected strains, as well as the high mutation rate, must be connected with regular changes in the spectrum of retrotransposons (MDG1, MDG3) and hobo elements characteristic of the strains studied. A special crossing system that induces a sharp increase in LA induction potential in the H-E system of hybrid dysgenesis was developed.