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.