Investigations on radiosensitive and radioresistant populations of Drosophila melanogaster. XIV. The genetic factor rar-1: effects in immature oocytes and their inhibition by caffeine.

The genetic factor rar-1 is part of the system of relative radioresistance that has evolved in the irradiated population ROI4 of Drosophila melanogaster. Previous data tentatively indicated an inhibition of rar-1 by caffeine. The present work was devoted to an extension of these caffeine studies to various end-points of genetic radiation damage induced at various exposure levels in immature oocytes of ROI4, of the contemporaneous control population Berlin wild K, and also in those of a substitution stock that carries rar-1 but not the other factors of relative radioresistance in ROI4, namely rar-2 and rar-3. The results show that it is the effect of rar-1 which is inhibited by caffeine. They confirm that rar-1 affects pathways of mutagenesis which produce recessive and dominant lethals but not chromosome losses.