An attempt to estimate the induction by X-rays of recessive lethal and visible mutations in mice

Abstract

The experiment was designed to form a bridge between the results of specific-locus experiments, using only a few gene loci, and those using the whole genome of the mouse. Male mice were given 600 r acute X-rays and bred from in such a way that at successive stages mutation in spermatogonia to dominant visibles and lethals, dominant semisteriles, recessive visibles and recessive lethals could be measured. The data concerning dominant mutations were relatively few but confirmed previous results. No recessive visible mutations were found, and the upper fiducial limit to the induced mutation rate to recessive visibles was set at a value 4500 times the rate to viable specific-locus mutations. From the attempt to measure recessive lethal mutations two interesting points emerged. The first was that granddaughters of the irradiated males had fewer corpora lutea per pregnancy than granddaughters of the control males, and the second was that this difference in number of ova shed was not reflected in any difference in litter-size at birth. Since this suggests intra-uterine compensation, no attempt was made to calculate mutation rates to recessive lethal genes from these data. The implications of the results are discussed.