The Induction of Mutations in Spermatocytes ofDrosophila Melanogasterwith X-rays

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Abstract
F1 males of Drosophila melanogaster have been irradiated with 1000 rads x-rays and then mated at the rate of two females per male per day for eight days following the irradiation. The frequencies of dominant lethals, translocations, sex-linked lethals, deleted X''s and induced crossing-over in the male have been estimated in on days 5, 6, 7 and 8 following treatment. It is claimed that the sperm used in matings over these four sampling days was in the spermatocyte or early spermatid stage at the time of irradiation. Thus the frequencies of mutations recorded will give an estimate of the relative sensitivities of these various stages of germ cell development to x-rays. Results show that sex-linked lethals and translocations follow similar patterns, reaching a peak on day 5, the level then dropping off through days 6 and 7 to a low value on day 8. Dominant lethals show an in-crease from day 5 to a high level on day 6 which is maintained over days 7 and 8. Deleted X''s and induced crossing-over increase from day 5 through days 6 and 7 to reach a peak on day 8. The relationship between the type of aberration studied and the sensitivity pattern of the treated germ-cells is discussed.