Induction of mosaic sex-linked recessive lethals in the different germ cell stages of Drosophila melanogaster by bleomycin

Abstract

The mutagenicity of bleomycin was studied in the different stages of spermatogenesis in Drosophila melanogaster. Following the injection of 2 μl of 0.1 μg/ml of the chemical into young wild-type males, complete and mosaic sex-linked recessive lethals were scored by the Muller-5 method in five successive broods, mainly representing the different stages of spermatogenesis. The delayed mutagenic effect of the chemical was measured by the proportion of mosaic progeny produced. The results showed that bleomycin significantly increased the proportions of both complete and mosaic lethals in the broods representing the meiotic and pre-meiotic stages, but did not show any significant increase in these proportions in the broods representing the sperms and spermatids. The sizes of the mutated areas in the F 1 gonads represented by the proportions of lethal-bearing females in F 2 mosaic cultures were small, indicating that the genetic instabilities induced by bleomycin were transformed into actual mutations in later zygotic divisions. The significant production of mosaic progeny in the F 4 generation of the treated males showed that the mosaic F 1 females produced by bleomycin were able to produce further mosaic progeny and suggested that bleomycin-induced instabilities can be transmitted as such for many future generations.