A new wild-derived H–2 haplotype enhancing K–IA recombination

Abstract

It is generally accepted that the overall recombination frequency between the H–2K and H–2D loci of the mouse major histocompatibility complex (H–2) is at a low level of about 0.4%¹. However, the value fluctuates depending upon the combinations of H–2 haplotypes in the heterozygote¹. We re-examined the intra-H–2 recombination frequency, using three B10.W congeneic strains which carry the H–2 complex of Japanese wild mice. Of the three, one strain, B10.MOL-SGR(H–2^wm7), showed an extremely high incidence of recombination (about 3%) in all combinations with three different inbred B10 congeneic strains. The serological typing of these recombinants revealed that most of the crossing-over points had occurred between the H–2K and IA loci. These results suggest that the wm7 haplotype enhances specific recombination irrespective of H–2 partners in heterozygous parents.