DEPENDENCE OF MUTATION FREQUENCY ON RADIATION DOSE RATE IN FEMALE MICE.

The specific locus mutation rate in females is significantly higher following acute than following chronic irradiation. Since conditions in the adult mouse ovary are such that complications from secondary factors are unlikely, it can be concluded that in oocytes there is a dose-rate effect on the mutation process itself. The influence of dose ratc on the frequency of mutations following irradiation of spermatogonia, which was demonstrated earlier and which could have been due to secondary factors, is now, in the light of the oocyte results, also considered to be due to a dose-rate effect on the mutation process. The most significant features of the results, from the point of view of human hazards, are, first, that there is, at present, no evidence that females are less sensitive than males and, second, that the finding of a dependence of mutation frequency on radiation dose rate, now extended from males to females, applies to those germ cell stages that are important in human hazards. (auth)