Abstract: In this study, the exon 2 of MHC-DRB3 gene was amplified by PCR and a uniform fragment of 285 bp was obtained in four sheep breeds(Aletai sheep, China merino sheep and hu sheep, Dorset sheep).The 285 bp PCR product was digested with restriction endomuclease PstⅠ,TaqⅠand HaeⅢ, and genetic polymorphism were investigated by PCRRFLP. The results indicated that it had polymorphisms in the 122th, 154th, 168th, 220th and the 237th.The χ2 tests showed that PstⅠrestriction enzyme sites were HardyWeinberg equilibrium in all sheep population, TaqⅠand HaeⅢ restriction enzyme sites were not Hardy-Weinberg equilibrium in four sheep population. The Gene heterozygosity is 0.693~0.774 and polymorphism information content is 0.662~0.738 in four sheep breeds, the results showed that the genetic diversity of four sheep breeds are rich; Clustering analysis showed that China merino sheep had the closest genetic relationship with hu sheep, further with Aletai sheep and Dorset sheep,it is the same with breed selection,and can do further reacher on the Polymorphisms of MHC-DRB3 Gene as the sheep breeding marker.

Key words: sheep; MHC-DRB3; PCR-RFLP; genetic polymorphism