Mutation in Ontogene and Emergence of Secondary Chromosome Damages in Drosophila Germline Cells

The conditional mutations in drosophila were obtained by γ-irradiation and selected using the test for dominant lethality. The conditional mutations survive under permissive genetic conditions and, additionally, commence to display novel properties. One of such properties is a recessive lethality. Ten conditional mutations that displayed recessive lethality were mapped with the help of a standard set of deletions. Half mutations contained two and more lethal defects. The fact that a large number of the lethal defects are associated with one mutation suggests that γ-irradiation is the most unlikely cause of the defects. One of the conditional mutations carried four lethal regions and had a Small barrel (Smba) visual phenotype. The Smba phenotype in the Smba/ In(2LR) Cy strain is inherited according to a parental type and disappears in the Smba/In(2LR) Pm strain. Lethality in two of the four lethal regions also disappears in this strain. A separate experiment was conducted to clarify how these regions lost a lethal manifestation after the In(2LR) Cy chromosome in the Smba/In(2LR) Cy strain was replaced with the In(2LR) Pm chromosome. The process of disappearance of the Smba phenotype was also observed in three Smba/In(2LR) Cy substocks. These data suggest that the regions of multiple recessive lethality emerge in a secondary manner under the effect of the earlier formed radiation-induced mutation in ontogene. It is assumed that the recessive lethal regions are the ontogenes with an altered DNA conformation. The conformation in ontogenes is changed in the germline cells during a regular “editing” of the individual development program.