A sex-transformation gene in Drosophila melanogaster.

A sex-transformation gene, tra-2OTF, of Drosophila melanogaster is described. The gene is an allele of tra-2 (transformer-2, 7--70+/-), acts only on XX individuals and transforms them into morphologically nearly normal but sterile males. Neither a male-specific lethal gene mle nor the male-killing maternally transmitted infectious SR-agent have any effect on the tra-2OTF transformed flies. External as well as internal reproductive organs of tra-2OTF transformed flies, except for the gonads, are male. The gonads, which are yellowish-colored rudimentary testis-like structures in tra-2 transformed flies, are rudimentary ovaries without yellowish coloration that sometimes develop to near maturity. Numbers of bristles in each of the female pattern in tra-2OTF and tra-2OTF/tra-2 transformed flies, while these bristles are of the male pattern in tra-2 transformed flies. Furthermore, the sixth abdominal sternite, which in normal males as well as in tra-2 transformed males lacks bristles, bears numbers of bristles in tra-2OTF and tra-2OTF/tra-2 transformed flies.