MATERNAL INFLUENCE ON POSTIMPLANTATION SURVIVAL IN INBRED RATS

Abstract

The effect of genotype in determining the increase of post-implantation mortality was studied in an inbred ACI rat strain. This mortality could be due to a defective embryonic genotype, a lethal maternal effect or an interaction of the two. Through various inbreeding experiments and embryonic examination after implantation at 12 days, the genetic mechanism appears to be limited to females and may be sex-linked or a group of multiple genes acting in concert. An autosomal or sex-linked dominant gene with complete penetrance is not compatible with a low rate of embryonic mortality in those combinations involving hybrid females. Embryonic mortality occurs early in gestation, and thus the effect of the maternal genotype on post-implantation mortality is the failure of the maternal uterine environment to support the pregnancy rather than a defect in the genetic constitution of the embryo.