A COMPARATIVE-ANALYSIS OF MHC DRB3 POLYMORPHISM IN THE AMERICAN BISON(BISON-BISON)

The degree of genetic polymorphism at the DRB3 locus in the major hist ocompatibility complex (Mhc) of the North American bison was investiga ted by PCR and DNA sequence analysis, Nine different alleles were char acterized in a selected sample of 20 animals, The genetic distances be tween alleles were as large as usually found at highly polymorphic Mhc loci in other species, A comparative analysis of the DRB3 polymorphis m in bison and cattle revealed an extensive sharing of sequence motifs . The result clearly shows a transspecies persistence of DRB3 allelic lineages in the two species, Consequently a significant amount of Mhc polymorphism has been maintained through the population bottleneck tha t bison experienced in the late nineteenth century, An analysis of the pattern of sequence polymorphism among bison and cattle DRB3 alleles strongly suggested that interallelic recombination has contributed sig nificantly to the generation of allelic diversity at this locus.