Analysis of recombinational hot spots associated with the p haplotype of the mouse MHC.

Most of the recombination events detected within the major histocompatibility complex (MHC) of the mouse fall into areas of limited physical size that have been designated recombinational hot spots. One of these hot spots, associated with the Ea gene, appears to be active only in the presence of the p haplotype of the MHC. To study the regulation of the Ea recombinational hot spot and its haplotype specificity, a high-resolution comparative map of the MHC and adjacent regions was completed in four different backcrosses carrying the p haplotype. This mapping study utilized a total of 29 PCR-based molecular markers, including 7 newly developed markers spanning the region between Pim1 and D17Mit11 on Chromosome 17. The analysis of a total of 1093 backcross animals: (1) revealed that the presence of the p haplotype of the MHC is not sufficient to induce recombination at the Ea hot spot in a dominant manner, and (2) resulted in the definition of a new intra-MHC recombinational hot spot between the Tnfb and the H2-D genes.