Relative Time of Eclosion of Drosophila Females Heterozygous for Sex-Linked Recessive Lethals

Abstract

Male D. melanogaster (Oregon-R) were irradiated with 3200 rads of 1.6 mev electrons and mated to Muller-5 females. The ecloeing F1 female progeny were collected at 12-hour intervals and tested for the presence of sex-linked recessive lethal mutations in the irradiated X-chromosome. The probability that an emerging female possessed a lethal X-chromosome was found to increase significantly in each successive period of collection. Assuming a linear response, a weighted linear regression analysis of the data leads to the equation Y = 5.342 + 1.338 X, where Y is the expected percentage of lethais and X is the sequential collection period. These results suggest that newly-induced recessive lethals tend to prolong development in heterozygotes, and that at least part of the viability impairment of heterozygous lethals is a reflection of decreased developmental rate.