Investigations on radiosensitive and radioresistant populations of Drosophila melanogaster. XI. The resistance factor rar-3: effects in immature oocytes.

The effects of the radioresistance factor rar-3 on the X-ray induction of various types of genetic damage in immature oocytes (about stage 7) of Drosophila melanogaster were studied. The dose-reduction factors previously postulated for rar-3 with respect to dominant lethals (1.58), sex-linked recessive lethals (1.87), non-disjunction of major chromosomes (1.58), and homologous interchanges (1.58) were confirmed experimentally. It is concluded that all effects attributed arbitrarily to rar-3 are contributed by the single genetic factor rar-3. No differences were found in quality of sex-linked recessive lethals (Y suppression, distribution over the X) induced in either rar-3 or rar-3+. Recombination frequencies were normal in unirradiated rar-3.