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GENETIC ANALYSIS OF H‐2 LINKED GENE(S) AFFECTING EARLY MOUSE EMBRYO DEVELOPMENT

The number of cells in preimplantation mouse embryos of different H‐2 haplotypes was analysed. It was found that embryos of the H‐2k haplotype have fewer cells per embryo than those of the H‐2b haplotype. By analysing reciprocal congenic pairs of mice it was demonstrated unequivocally that slow development is linked to the H‐2k haplotype and fast development to the H‐2b haplotype. The gene(s) in the H‐2 complex which influence early mouse embryo development have been named Ped: preimplantation embryo development. Analysis of F1 hybrid embryos showed that fast development is dominant. Reciprocal F1 crosses yielded identical results, which indicated there was no apparent effect of the maternal egg cytoplasm on Ped gene expression. Analysis of F2 and back‐cross embryos was consistent with the interpretation that there is a major gene located in the H‐2 complex (Ped), which is modified by environment and genetic background, that influences early mouse embryo development.