Interaction of mutational lesions induced by ethyl methanesulphonate and γ - rays in males of drosophila

Abstract

Post γ-irradiation EMS treatment enhanced the frequency of sex-linked recessive lethals and translocations in Drosophila males. The mutation frequency observed in the combined treatments was significantly greater than that obtained by adding the frequencies produced by the two treatments individually. The synergism in mutation frequency was not due to the selective elimination of some of the cell stages but to a higher proportion of mutated sperm per affected male. It is suggested that the increase in mutation frequency was due either to a more efficient induction of premutational lesions by EMS or to a more efficient fixation of these lesions by post-EMS treatment. Under the treatment conditions used, EMS did not induce translocations in mature spermatozoa, but when combine with γ-rays, the translocation frequency increased significantly over that produced by γ-rays alone. These results have been interpreted to mean that post-EMS treatment somehow checks the repair of radiation-induced breaks and thus increases the chance of their rejoining.