Induction of congenital malformation in mice by parental irradiation: transmission to later generations.

In order to investigate the genetic basis of the increased incidence of congenital malformations in the offspring of irradiated mice, the frequency of malformations among the offspring of individual F1 sons of irradiated females was studied in detail. Among 90 fully tested F1 sons of females which had been mated 15-21 days after receiving 360 cGy X-rays 4 were definite or probable carriers of dominant genes giving a low penetrance of malformations. This confirms that the malformations seen in the first generation are of genetic origin and can be transmitted to later generations. However, the incidence and penetrance of the mutant genes detected were too low to account for all the anomalies found in the first generation. It was concluded that the genetic basis of the original anomalies was heterogeneous, with some due to genetic changes of high penetrance and rapidly eliminated, and others due to genes of low penetrance like those found in this work. Other malformations, in both the irradiated and control series, were probably of non-genetic origin.