P-ELEMENT-INDUCED MUTATIONS IN DROSOPHILA-MELANOGASTER SHOWING HIGH INTERSPECIFIC CROSSABILITY BETWEEN DROSOPHILA-MELANOGASTER FEMALES AND DROSOPHILA-SIMULANS MALES

Homozygous stocks for the second or the third chromosome of Drosophila melanogaster with a single insertional plwB element were screened for high crossability with D. simulans. Reciprocal crosses between each o f these stocks and D. simulans were made, and the insemination rate at two or three days was examined. From two cycles of screening of the o riginal 575 stocks, one stock (# 687) which showed high insemination r ate was selected and was backcrossed to a w strain to substitute the b ackground. We obtained a stock which showed 10% insemination rate with D. simulans males (control was 0%). No stocks exhibiting a high cross ability with D. simulans females were acquired. Revertant strains, fro m which the P element had been lost, were obtained from the backcrosse d #687 stock. The insemination rates of 13 revertants to D. simulans m ales ranged from 1% to 33%. Seven of these 13 were not significantly d ifferent from the control line but were significantly different from t he backcrossed #687 stock. It was concluded that the mutation showing high crossability with D. simulans males was caused by the P element t ransposition.