Abstract
Male DBA/2J and C57BL/6J mice were treated with ethylnitrosourea (EtNU) at a dose of 250 mg/kg of body weight. After a sterile period of 11 weeks, the treated animals were mated with untreated females; treated DBA with C57 and treated C57 with DBA. A small control group of untreated males was established, and a larger control group from earlier experiments was also used for comparison. Tissue samples removed surgically from the parents and F1 offspring were examined by electrophoresis. Nine newly arisen mutants attributable to induction by EtNU were found in 22,512 loci tested for mutation. No mutations were encountered in 290,252 control locus tests. A preliminary study conducted concomitantly with the electrophoretic analyses for dominant lethal effects and physical malformation showed no increase over background due to EtNU treatment of spermatogonia, which suggests that mutations induced by EtNU tend not to be expressed in this way. The nature of the mutants identified by electrophoresis facilitates follow-up analyses leading to increased understanding of the molecular basis and the physiological effects of induced mutations in mammalian organisms.