Observations on Lifespan, Radioresistance, and Productivity in Offspring from 5 to 25 Generations of X-irradiated Male Mice.

T H E requirement for research to determine some of the general and specific genetic effects of X irradiation to consecutive generations of mammals was stressed by The UNITED NATIONS CIENTIFIC OMMITTEE ON THE EFFECTS OF ATOMIC RADIATION (1958). In response to this need a program was started to investigate possible nonspecific effects of X irradiation to consecutive generations of male mice. This program was designed with full awareness that there are as many approaches to the problem as there are investigators willing to undertake such a task, and with appreciation of our then present and projected facilities and personnel. One of the primary objectives of this program was to do comparative studies on control-line and X-irradiated-line mouse populations after several generations of X-ray exposure. For this reason it was desirable to start the two lines with the smallest amount of heterozygosity possible. No attempt has been made to preserve “recessive” mutations or to estimate the frequency of lethals, and although X-ray exposures were given primarily at the prespermatid stage of germ cell development, a few offspring may have been propagated from sperm irradiated as spermatids. The following are observations on lifespan of mice from 5, 10, and 15 generations of X-irradiated parentage, productivity of mice from 20 generations of X-irradiated parentage, and radioresistance of mice from 25 generations of Xirradiated ancestors.