The ineffectiveness of chronic irradiation with neutrons and gamma rays in inducing mutations in female mice.

Abstract

Hybrid female mice were exposed to 412 rads 60Co γ rays or 80 rads fast neutrons (+ γ contamination) in 12 weeks and the amount of genetic damage in offspring was compared with controls. Frequencies of specific locus recessive and of dominant visible mutations were very low in the irradiated series, differing little from the control frequencies of nil. There were no significant differences between the sex-ratios of offspring in the three series, thus no evidence for the induction of sex-linked lethal mutations. No estimates can be given of the relative genetic effectiveness of chronic neutron and γ exposures in female mice, but the specific locus mutation frequency after the neutron dose was less than 5 per cent of that obtained in male mice after spermatogonial irradiation with a similar dose over the same 12-week period. It is now clear that both acute and chronic exposures of the immature mouse oocyte to both high and low LET radiations result in minimal genetic damage. It is still not clear whether this applies to the human oocyte also.