Recessive lethal mutation induced in the mouse by chronicγ-irradiation

Abstract

When the sons of irradiated mice are mated to their own daughters, the average size of the ensuing litters will depend on the number of recessive embryonic lethal genes segregating; it can therefore be used to estimate the rate of induction of recessive lethal mutation by the radiation, provided that one can show that any change is not due to dominant sublethals or semisteriles. Data from an experiment in which mouse sperm were exposed to low accumu­lated doses of radiumγ-radiation lead to an estimate of one recessive lethal per 300 roentgen. This is 23 times the corresponding rate forDrosophila melanogaster. It may be compared with the results reported by Russell (1952), who found that the rate of induction of recessive visibles per locus in mouse spermatogonia is 15 times theDrosophilarate; and with those of Vendrely (1955), who found that mouse nuclei have 29 times as much desoxyribonucleic acid asDrosophilanuclei. It is suggested that the mouse may have only slightly more genes thanDrosophila, but that each may be about 19 times as large and, for this reason, about 19 times as sensitive to radiation-induced mutation. Implications for human radiogenetic studies are discussed.