The nature of X-ray-induced mutations in mature sperm and spermatogonial cells of Drosophila melanogaster.

Mutations at four X-linked visible loci (yellow, white, vermilion and forked) induced by X-irradiation of mature sperm and spermatogonial cells were analysed genetically and cytogenetically. In addition, a fraction of the intragenic vermilion mutations was analysed molecularly. Males of two wild-type strains (Amherst M56i and Berlin-K) were used. A total of 332,651 chromosomes of irradiated mature sperm and 311,567 of irradiated spermatogonial cells were scored. The ratio of F1 female sterile, F2 male lethal and F2 male viable mutations in mature sperm and spermatogonial cells is very similar. The cytogenetic analysis shows equal fractions of multilocus deletions and translocations among the mutations recovered from both stages of spermatogenesis. These data strongly suggest that the spectrum of X-ray mutations is similar in mature sperm and spermatogonial cells, including multilocus deletions and chromosome rearrangements. The molecular analysis of a number of intragenic vermilion mutations showed the presence of three small deletions (1-10 bp), one insertion of two nucleotides and seven single nucleotide changes.