Lifetime reproductive capacity in offspring of an irradiated mouse population

Abstract

Unirradiated offspring of the 14th generation of an irradiated mouse population in which the males of each generation had received 276 R to the spermatogonia, and offspring of the parallel control population, were tested in single pair matings for lifetime reproductive performance. The offspring of the irradiated population showed a significant tendency towards lower age at 1st litter which was interpreted as a sign of earlier sexual maturity. This group also exhibited an overall mean litter size lower than that of the control which was attributable to the presence of semisterile animals among the pairs tested. An examination of the sex proportion based on the total materials showed a significant downward shift for the irradiated population offspring when compared with the control. However, pedigree studies and analysis of sex proportion in relation to litter size led to the conclusion that the observed change was not due to the presence of sex-linked recessive lethals. The overall effects of ancestral irradiation on reproduction were found to be exceedingly small, which was in keeping with results obtained from other studies of irradiated populations. It was therefore concluded that a reduction of reproductive capacity may not play any great role as a selective factor in the removal of induced genetic damage from an irradiated population.