Influence of a Single Mutation on the Incidence of Pregnancy Block in Mice

It has been shown that major histocompatibility complex (MHC) types affect the mating choices of mice and that mice can be trained to distinguish arms of a Y maze scented by odors from MHC-congenic mice or their urines. To investigate the relevance of H-2K genetic variation to reproductive behavior, the authors have now tested the effect of isolated H-2K genetic variation in the circumstances of "pregnancy block". Pregnancy block (the Bruce effect) refers to determination of pregnancy before implantation of the embryo (before day six of gestation in the mouse) after exposure of the female to an unfamiliar male, particularly of a strain different from the stud male.