A GENETIC-CHARACTERIZATION OF DIFFERENCES IN THE SENSITIVITY TO RADIATION-INDUCED MALFORMATION FREQUENCIES IN THE MOUSE STRAINS HEILIGENBERGER, C57BI, AND HEILIGENBERGER X C57BI

We studied the frequency of malformations induced in two mouse strains (Heiligenberger, C57B1/6J) by exposure to x-rays 3 h after conception . Whereas there was a high number of malformed fetuses in Heiligenberg er mice (mostly gastroschises) on day 19 of pregnancy, C57B1 did not r espond to radiation exposure shortly after conception with an increase d frequency of malformed fetuses. Cross-breeding of both strains revea led that no statistically significant increase in radiation-induced ma lformations was obtained in the F-1 fetuses when the father was Heilig enberger and the mother C57B1, In the opposite case (Heibligenberger m other, C57B1 father) a small but statistically significant increase wa s observed.