H-2-associated differences in androgen-influenced organ weights of a and C57BL/10 mouse strains and their crosses

The influence ofH-2 haplotypes (in three-month-old males) on body weight, vesicular gland, testes, and thymus weight was investigated in A, B10, and B10.A strains and their respective F1, F2, and Bc progeny. The influence of theH-2 haplotypes was found to contribute to heterosis in the body weight.H-2a/H-2a males have a smaller vesicular gland and larger testes and thymus weight thanH-2b/H-2b males when groups with an identical or comparable genetic background are compared.H-2 heterozygous classes are closer to the parental strain with higher values for absolute organ weight; for relative organ weight, the heterozygous classes are intermediate or closer to the parental strain with lower values. This complex situation results from the simultaneous action ofH-2 haplotypes on both organ weight (Hom-1 effect) and body weight (heterosis), which probably operate through different mechanisms. Coat color genes were found to modify the penetrance ofH-2 influence on quantitative traits.