EA RECOMBINATIONAL HOT-SPOT IN THE MOUSE MAJOR HISTOCOMPATIBILITY COMPLEX MAPS TO THE 4TH INTRON OF THE EA GENE

The majority of recombination events detected within the mouse major h istocompatibility complex (MHC) Fall into regions of limited physical distance known as hot spots of meiotic recombination. The hot spot ass ociated with the Ea gene appears to be active only in the presence of the p allele carried by the intra-MHC recombinant strain B10.F(13R). T o study the frequency, regulation, and haplotype specificity of recomb ination at the Ea hot spot, progeny from three different backcrosses i nvolving B10.F(13R) were screened for recombination events across the MHC using DNA microsatellite markers. Screening of a total of 750 back cross progeny permitted the identification of seven recombinants withi n the Ea gene. Using restriction site polymorphisms, and sequence-base d nucleotide polymorphisms, the recombination breakpoints in all seven Ea recombinants were mapped to two adjacent segments of 71 bp and 346 bp in intron 4 of the Ea gene.