The Effect of Oxygen Concentration on the Rate of X-Ray Induced Mutations in Drosophila

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Abstract
Two groups of wild-type males, maintained in O2 and N2 gas respectively were exposed to X-rays of 1000 r, 3000 r, and 5000 r at known constant temps. They were mated to virgin Muller-5 females (scsl B In-S wa sc8) and the F2 and F3 were examined for recessive sex-linked lethal mutations. In 31 individual expts. the reduction in mutation rate in the N series compared to the O series was highly significant except when the flies were given 1000 r and kept at a warm temp. Irradiation in an 02 atmosphere produced more mutations at temps. of 0.5-3.0[degree]C. than at 22.0-29.0cC, whereas in the N series the temp. difference had no apparent effect. A reduced no. of offspring per culture produced by males irradiated while in O2 as compared with N2 was believed due to a higher frequency of induced dominant lethal mutations. The reduction in mutations in the N series is apparently due to a lowered 02 tension in the sperm of treated flies, and in the O series the higher frequency of mutations at the low temp. is not due to the temp. per se but to the higher O2 tension within the sperm.