An analysis of translocations in the mouse.

ADIATION-INDUCED translocations in the mouse have been studied R by SNELL, BODEMANN, and HOLLANDER (1934)~ SNELL (1935, 1939, 19418, 1941b), SNELL and PICKEN (1935)~ SNELL and AMES (1939), HERTWIG (1938, 1940)~ KOLLER and AUERBACH (1941), and ROLLER (1944). The results of SNELL and co-workers have been summarized elsewhere (1941a). HERTWIG (1940) has made a very thorough and detailed investigation of prenatal mortality, litter size, and inheritance of semi-sterility in 11 out of a total of 60 semi-sterile lines derived from irradiated males. The prenatal mortality was determined from sections of the uteri and ovaries of 300 normal females mated to semi-sterile males and killed ten days or less post-coitus. The sectioned uteri and ovaries of 211 normal femalesxnormal males served as controls. Embryos were classified as normal, dead embryos, large implantations (that is, large uterine swellings containing only the remains of an embryo), and small implantations. A corpus luteum count indicated the number of ova fertilized, or a t least available for fertilization. In the semisterile group, the embryos showed 36.10 k0.91 percent survival (number of normal embryosx Ioo/number of corpora lutea) ; in the control group the figure was 75.37ko.99 percent. Hence the fertility of the test animals was slightly less than 50 percent of the fertility of the controls. The fertility of the test animals may be calculated also from the size of litters carried to term. The mating of semi-steriles, both males a& females, from 11 translocation stocks,Xnormals gave 1462 litters with a mean litter size of 3.12 10.002. Comparable normal matings gave 790 litters with a mean litter size of 6.861 0.064. The fertility of the translocation heterozygotes is, therefore, 45.48 percent that of normal mice. Again the fertility is reduced by slightly more than one-half. This is the average figure for the 11 different stocks. Taking the stocks separately, the fertilities for the different translocations each in terms of its control are: 41.8 percent, 42.9 percent, 44.2 percent, 45.2 percent, 45.7 percent, 46.3 percent, 48.1 percent, 49.1 percent, 50.6 percent, 52.2 percent, 58.7 percent. If these figures are broken down still further according to which parent is the heterozygote and to whether, in the case of male heterozygotes, the female is a sister or unrelated, there is seen to be a considerable lack of consistency in the data. Hence the significance of the individual percentages is somewhat open to question. Nevertheless, a tendency for a t least some translocations in the mouse to cause a reduction in fertility to something less than 50 percent of normal is very strongly indicated. The litter size for the mating translocation heterozygotextranslocation heterozygote was also investigated and found to be 37.17 percent of normal (average figure for 11 stocks).