Tests on Drosophila for the Production of Mutations by Irradiated Medium or Irradiated DNA

Abstract

(1) Irradiated medium. Ionizing radiations are likely to find increasing use in industry for prolonging the useful storage-life of food. Before the method is declared safe and becomes widely acceptable, however, it is necessary to ensure that consumption of irradiated food is free from genetic ill-effects. Mutation rates have been shown to increase when bacteria are grown in ultra-violet-irradiated substrate¹. Bacterial medium irradiated with ionizing radiations, however, has not been tested for its mutagenic effects. Information about the indirect genetic effects of ionizing radiations in higher organisms is scanty. Investigations of the cytological effects in root meristems of plants grown in X- and γ-ray irradiated potato mash² and fruit juices³ have shown that the aberration frequencies in treated roots were strikingly higher than in corresponding controls. In order to test for similar effects in animals, these studies were extended to Drosophila. It was found that the rate of sex-linked lethals was increased slightly, but significantly, in the progeny of flies raised on irradiated food⁴. In view of the obvious importance of this observation it was thought necessary to re-test it, scoring both autosomal and sex-linked lethals. The former were included because it has been shown^5,6 that feeding of unirradiated calf thymus DNA has a very specific and pronounced mutagenic effect on chromosome II of Drosophila, while the X-chromosome remains largely refractory to this treatment. Induced dominant lethality was also investigated in view of the chromosome breakage observed in plant material grown on irradiated medium. The results of these investigations are reported in this communication.