H-2-associated differences in replicated strains of mice divergently selected for body weight.

A random-bred strain (Q) was established and divided into six replicates. Each replicate was divergently selected for 6-week weight (for over 30 generations) and each had an unselected control. We have investigated the H-2 haplotype of individual mice of the 18 selected Q strains to determine whether selection for size had also selected for H-2 or H-2-linked genes. From the results it appeared that only the H2b and H-2q haplotypes were present in the foundation stock. A large number of individuals of the six small sublines were of H-2b haplotype, while the majority of those of the six large sublines were of the H-2q haplotype. Individuals in the six control strains were H-2b, H-2q or both (i.e., H-2 heterozygotes and/or H-2 recombinants). These results suggest that control of body size is associated with H-2 or an H-2-linked gene(s).