A small region on the X chromosome of Drosophila regulates a key gene that controls sex determination and dosage compensation.
In Drosophila, flies with two X chromosomes are females, with one X chromosome, males. We investigated the presence of sex determining factors on the X chromosome by constructing genotypes with one X and various X-chromosomal duplications. We found that female determining factors are not evenly distributed along the X chromosome as had been previously postulated. A distal duplication covering 35% of the X chromosome promotes female differentiation, a much larger proximal duplication of 60% results in male differentiation. The strong feminizing effect of distal duplications originates from a small segment that, when present in two doses, activates Sxl, a key gene for sex determination and dosage compensation. Our results suggest that Sxl can be activated to intermediate levels.
D000782:Aneuploidy; D000818:Animals; D004331:Drosophila melanogaster / Q000033:anatomy & histology / Q000235:genetics*; D005260:Female; D005796:Genes; D005804:Genes, Lethal; D005838:Genotype; D007814:Larva / Q000166:cytology; D008297:Male; D012469:Salivary Glands / Q000166:cytology; D012732:Sex Determination Analysis; D014960:X Chromosome