Studies on the sex-specific lethals of Drosophila melanogaster. IX. Characterization of fle(3)100, a female-specific lethal mutation.

A female-specific late-lethal mutation, fle(3)100, of Drosophila melanogaster was examined on its effects in XX-XO mosaics, and its interaction with various alleles of sex-determination genes tra-2 and dsx. Mosaic flies homozygous for fle(3)100 appeared at a high frequency (more than 80%) compared to the control heterozygous flies. Mosaics, however, rarely appeared when they had relatively large XX tissues. A significant reduction of the frequency of XX genotype was observed in the second and third abdominal sternites, suggesting the presence of a focus or foci of primary gene action in the internal organ or tissue near these structures on the blastoderm fate map. Chromosomal females doubly homozygous for fle(3)100 and tra-2 or dsx were not rescued. Females homozygous for fle(3)100 as well as those doubly homozygous for fle(3)100 and tra-2 died as pharate adults. Unexpectedly, chromosomal males doubly homozygous for fle(3)100 and tra-2 showed variations in viability ranging from about 20% to 100% depending on the alleles of the tra-2 locus examined. These males also died as pharate adults.