Abstract: In this paper, the genetic polymorphism of the exon 2 of MHC-DQB gene was investigated by directly sequencing and PCR-RFLP in Yunnan humped cattle. Homology of the nucleotide acid sequences was analysis by DNAMAN software. The results showed that 17 alleles were found in this experiment,10 kinds of genotypes and 5 (A, B, C, D, E) alleles were found with enzyme Hae Ⅲ;22 kinds of genotypes and 11 (A, B, C, D, E, F, G, H, I, J, K) alleles were found with enzyme RsaⅠ;only one kind of genotype were found with enzyme TaqⅠ. Polymorphic sites were detected at base position 12, 25, 63, 96, 106, 126, 152, 156, 165 and 204. The results showed that there were same lengths (270 bp) of gene fragment in various species, but there was a nucleotide missing at position 224 and a nucleotide insertion at position 236 in Yunnan humped cattle. The homology between Yunnan humped cattle and human, swine, horse, sheep, Yellow cattle × Zebuand were 81.4%, 83.3%, 78.1%, 87.7% and 86.6%, respectively. The results of χ² test showed that the polymorphic loci of Hae Ⅲ and TaqⅠwere in Hardy-Weinberg equilibrium (P＞0.05), but the locus of RsaⅠ was not in equilibrium (P＜0.05).

Key words: Yunnan humped cattle; MHC; DQB gene; exon 2; genetic polymorphism