Synergistic interaction between particular X-chromosome deletions and Sex-lethal causes female lethality in Drosophila melanogaster

Abstract

We studied the effect on female viability of trans-heterozygous combinations of X-chromosome deficiencies and Sxl ^f1, a null allele of Sex-lethal. Twentyfive deficiencies, which together covered 80% of the X chromosome, were tested. Seven of these trans-hcterozygous combinations caused significant levels of female lethality. Two of the seven interacting deficiencies include the previously known sex determination genes sans fills and sisterless-a. Four of the remaining uncover X-chromosomal regions that were not hitherto known to contain sex determination genes. These newly identified regions are defined by deficiencies Df(1)RA2 (7D10; 8A4-5), DJ(1)KA14 (7F1-2; 8C6), Df(1)C52 (8E; 9C-D) and Df(1)NI9 (17A1; 18A2). These four deficiencies were characterized further to determine whether it was the maternal or zygotic dosage that was primarily responsible for the observed lethality of female embryos, daughterless and extra macrochaetae, two known regulators of Sxl, influence the interaction of these deficiencies with Sxl.