AbstractThe induction of dominant lethal mutation in germ cells is the cause of embryonic death resulting in the reduction of litter size in the F1progeny. Dominant lethal mutations were induced when male mice were infected with live A2influenza virus. The chromosomal aberrations induced in the germ cells were shown to be responsible for the dominant lethality. Killed influenza virus was also potent in inducing chromosomal aberrations in spermatocytes of mice. In light of these observations, the UV‐inactivated virus was tested for its potency in induction of dominant lethality in both female and male germ cells. The virus‐inoculated females were mated with uninjected males and vice versa. Both the inactivated and live virus were found to induce dominant lethality in both female and male mice, indicating that not only the live virus but also the inactivated virus is capable of bringing about chromosomal damage resulting in dominant lethal