The Induction by Irradiation with Neutrons of Hereditary Changes in Mice.

In a previous paper by Snell and Aebersold' the production in male mice by irradiation with neutrons of an initial period during which small litters are sired, followed by a period of complete sterility, followed, in turn, for the smaller doses, by a resumption of normal fertility, has been described. This paper is concerned with the appearance of sterility and of heredity changes in the descendants of the irradiated males. The twelve irradiated males were from the C stock, homozygous for the mutant genes b and c. Before the onset of sterility they were mated as often as possible to females of the P stock (genotype aabbCCddppscs6), or in a few cases to females of the M stock (genotype aabbCCd2d2ppsese). F1 animals were mated to mice of the P (or M) stock to give the second generation, designated as the F2. F2 mice of the appropriate sex were selected and back-crossed and to their F1 parent to give the F3 generation, among the individuals of which new recessive mutations may be expected to become phenotypically visible if any such have been induced by the treatment. The advantages of this type of cross in a search for induced mutations have been discussed in a previous paper by Snell.2 In order to make a rapid test of the semi-sterility of F1 males, they were mated to females of the Pch stock as well as to the females from the P (and M) stocks. The Pch stock was selected because of its fertility. The results of the tests for sterility and semi-sterility are summarized in table 1.