Abstract: Objectives Analyzed genotype and allelic polymorphism of SLA-DQA gene extron 2 in Tibet mini-pigs to detect whether the genotype frequency of restriction enzyme sites was consistent with Hardy-Weinbeig equilibrium. Methods PCR-RFLP was used to analyze the partial sequences of intron 1 and intron 2 and the complete sequence of extron 2 of SLA-DQA in Tibet mini-pigs. Results The restriction enzyme map of EcoR I -RFLP site showed that the genotype frequency of BB(0.4500) was higher than that of AB(0.3167) and AA(0.2333), B was the predominant allele. As for the Alu I site, the genotype frequency of MN(0.5000) was higher than that of MM(0.3000) and NN(0.2000), and M was the predominant allele. According to the values of X2test (chi-square test), the genotypes at EcoR I site didn't reach the significance level(P＞0.05〕，while the Alu I site has significant differences (P＜0.05). Combined with double enzyme digestion result, there were 7 PCR-RFLP patterns of SLA-DQA gene in Tibet mini-pigs. The genotype frequency of BBMM(0.3000) was higher than other ones, while the genotype AANN or BBNN was not found. Conclusion The SLA-DQA gene of Tibet mini-pigs was not fit Hardy-Weinbeig equilibrium at Alu I site, and the genetic selection pressure of this site was higher than that of EcoR I site.

Key words: Tibet mini-pigs, SIA-DQA, PCR-RFLP, polymorphism