THE FREQUENCY OF XO MALES AND INDUCED AUTOSOMAL CROSSOVERS AFTER IRRADIATION OF DROSOPHILA MELANOGASTER MALES IN AIR OR COMMERCIAL NITROGEN

Abstract

Results are reported from an investigation of the frequency of induced XO males and induced autosomal crossovers in meiotic and premeiotic stages in Drosopltila after irradition of 0 to 1-day-old males. The effect of irradiation under anoxia upon the yield of XO males and upen the rate of induced autosomal crossovers was also studied during the period of highest sensitivity to x-ray irradiatibn. By use of a dual-purpose stock it was possible to study both aberrations in the same stock. It is shown that there is a significantly lower rate of induced XO males in experiments performed under anaerobic conditions compared to those irradiated in air. It is furthermore obvious that the difference is most drastic in mating periods corresponding to the highest sensitiviity. In order further to study the effect of irradition under anaerobic condltions two experiments were performed where the dose was divided into two parts. The first part consisted of 1100 r in commercial nitrogen with an interval of 15 and 60 minutes, respectively, in air, whereupon the second part, 700 r in air, was given. The results indicate that there is some recovery after irradiation of the sensitive stages but that it could be only partlymore » blocked by 700 r given in air within 15 minutes. That the reduced effect of irradiation under anoxia is not limited to XO males is obvious from the crossing- over study. The observed crossover data ftt well with the sensitivity pattern obtained through XO studies. Furthermore it is evident that spermatozoa available for insemination on the l2th day and onwards chiefly might correspond to cells treated as spermatogonia. (auth)« less