Effects of X-irradiation at different times during development on the yield of somatic mutations in melanocytes of the mouse

Abstract

The effect of 2.0 Gy X-irradiation at different times during foetal and early post-natal development on the resultant somatic mutation frequency was investigated by scoring for changes in follicular melanocyte morphology (nucleofugal vs. nucleopetal) in mice heterozygous for the recessive coat colour mutations dilute ( d) and leaden ( ln). Two peaks were observed following X-irradiation on days 12.5 and 17.5 post coitus (p.c.). The biomodal character of the mutation frequency with time of X-irradiation may be related to changes in the dynamics of the melanocyte population with foetal age. Nonetheless, the results validate the treatment time used in the pilot study (Searle and Stephenson, 1982) as the most sensitive to the induction of somatic mutations within the follicular melanocyte population.