Dose-rate and the Induction of Mutation inDrosophila

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Abstract
Drosophila male germ cells were exposed to 800 rad of 60Co γ-rays at three different dose-rates, 0·05, 0·5 and 5·0 rad/min. F0 males were mated in seven successive broods of which broods I and VII were sampled for IInd chromosome recessive lethal mutations. Mutation frequency was independent of dose-rate in each brood. It was concluded that dose-rate had no discernible effect on induced mutation frequency in spermatids (brood I) or spermatogonia (brood VII). These results are discussed in relation to the hypothesis that the dose-rate effect discovered by Russell in the mouse arose through repair of genetic radiation damage. It is suggested that killing of cells by radiation, which is much more extensive in the mouse than in Drosophila, would be a more plausible mechanism to explain the dose-rate effect than repair, for which there is no corroborative evidence.