A shift of sex-ratio in the progeny from irradiated males in drosophila melanogaster

Abstract

The present study was performed in order to investigate the sex-ratio changes in the progeny from males irradiated at different germ cell stages in Drosophila melanogaster. First, the result indicates that the sex-ratio (♀/♂) shifts to the lowest level when the progeny come from males of 6-8 days after irradiation, and recovers to the control level in the progeny from males of 14-16 days; and that the sex-ratio may be reduced with increasing dosage. In addition, it is noticeable that non-irradiated younger fathers produce more sons than daughters, a tendency which decreases with age. In the second place, the sex-ratio shift changed according to the frequency changes of both induced dominant lethals and elimination of sex-chromosomes, showing a negative correlation, and all the frequencies coincidentally reached a peak on the 7th-8th days after irradiation. The stage-frequency relationship for the sex-chromosome elimination is fundamentally the same as that for the dominant lethals, suggesting that the two phenomena might probably occur through the same mechanism. Next, in the present study the highest sterility was found during the 6th-8th days. All accounts suggest that sperm utilized during these days represents cells irradiated during the meiotic stages. Lastly, the proportion of X chromosome elimination (Se) and X chromosome dominant lethals (Sx) to the total shift of the sex-ratio (S) was estimated in each of the three different germ cell stages, i.e., post-meiosis, meiosis, and pre-meiosis. So far as the present data are concerned, the contribution of Se and Sx to S are nearly the same at the meiotic stages, while at the other stages Sx plays a greater part than Se. © 1967, The Genetics Society of Japan. All rights reserved.