Intra-H-2 recombinant congenic strains are widely used to localize traits to specific subregions of the major histocompatibility complex and have provided evidence for the existence of meiotic recombinational hotspots in mammals. Forty-seven intra-H-2 recombinant strains, including 12 not previously reported, have been identified by serological typing in our laboratory. We have extended the analysis of the cross-over sites in these mice using DNA markers for Ab, Aa, Eb, Ea, Cyp21-ps, D17Tu3, Bat7, and Bat5. The recombinant chromosomes of these congenic strains include loci derived from the a, b, f, k, p, q, r, s, u, and v haplotypes of H-2, providing a diverse panel of strains. Although some alleles of Bat7 could not be distinguished from one another, results from the majority of strains indicated a probable gene order of C4Slp/D17Tu3-Bat7-Bat5-H-2D. No recombinants between Cyp21-ps, C4Slp, and D17Tu3 were observed. The crossover sites in 31 of the 47 intra-H-2 recombinants were within the C4Slp/D17Tu3-H-2D interval; of these 31 crossovers, three were bracketed by D17Tu3 and Bat7, ten by Bat7 and Bat5, seven by Bat5 and H-2D, and 11 by D17Tu3 and Bat5. The results from all 47 strains suggest recombinational hotspots within the C4Slp/D17Tu3-H-2D interval and emphasize the influence that specific haplotypes can have on preferred crossover sites.
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