GENETIC-ANALYSIS OF THE CAUSE OF GASTROSCHISIS IN THE HLG MOUSE STRAIN

An inbred mouse strain HLG shows a high incidence of gastroschisis aft er X-ray exposure to the zygotes. About 11% of the fetuses display thi s malformation after irradiation with 1 Gy. The C57BL-strain does not show the increased frequency of gastroschisis after radiation-exposure to the zygotes. The genetic background of this malformation was inves tigated in a backcross of HLG X C57BL females to HLG males. The pregna nt HLG X C57BL females were irradiated in a stage in which the (HLG X C57BL)X HLG [BC1] embryos were in the 1-cell stage. The frequency of g astroschisis in the BC1 generation was compared with a genetic model o f a single recessive mutation with 11% penetrance. This frequency does not fit a single-locus inheritance. The number of loci involved was e stimated to be about two or three. HLG mouse strain may be a valuable animal model in the study of polygenic traits.