Identification of genetic variations of exon 2 of BoLA-DQB gene in five Chinese yellow cattle breeds.

One hundred and eighty animals from five Chinese yellow cattle breeds were used to identify genetic variations in the exon 2 of BoLA-DQB by polymerase chain reaction (PCR) followed by DNA sequencing analysis. A total of 35 alleles of BoLA-DQB including 19 newly identified ones were found. The number of alleles represents differences in breeds, indicating genetic variations among different breeds. The number of new alleles identified in this study suggests that the number of BoLA-DQB alleles is greater than what has been reported. The estimation of the average rate of synonymous (d(S)) and non-synonymous (d(N)) substitution in the exon 2 of BoLA-DQB showed there was a higher ratio of d(N) to d(S) substitutions in the peptide-binding site region, and such differences were significant in all five breeds P < 0.01).