| The major histocomapatibility complex (MHC) is a group of closely-linked and highly polymorphic gene in vertebrate animals. The gene encode the major histocompatibility antigen and plays a critical role in immune response. Due to its crucial role in animal disease-resistance, MHC has become an important research subject of human and animal husbandry. Mink is one of the major species of animals in the fur industry, and we have more than fifty years histories of farming minks in our country. Successful farming fur animal critically depends on the effective prevention of epidemic diseases, and immunological control is the most powerful way to achieve the aim. However, at present only few studies on mink immunity mechanism have reported. Therefore ,the current situation has seriously hindered the development of effctive means of prevention and treatment of these diseases. This research constructed the cDNA library ,which laid the foundation for the mink function gene clone and analysis; The mink MuLu-DRA gene cDNA sequence was cloned and analyzed for polymorphism, which provides the theoretical data for further study on the population evolution and the disease-resistace related candidate genes.(1) The full-length cDNA Library of American mink spleen was been constructed by using SMART (Switching Mechanism At 5 , end of RNA Transcript) technology. According to the results of phage plaques bright selection of host bacterial strain XL1-Blue and PCR detection, the percentage of recombinant phages were 91.1% and the titer was 1.07×109 pfu/ml, the library was of high quality for cloning target genes and expressing target proteins.(2) In order to study function and molecular polymorphism of MuLu-DRA gene of mink. Full-length of the cDNA sequence was 765bp, code 254 amino acid. The result of blasting indicated: the nucleotide had 97%,93%,93%,89%,88% identity with dog, cat, zalophus, homo spiens and macaca respectively; the deduced amimo acid had 96%,90%,93%,85%,85% identity with dog,cat,zalophus, homo spiens and macaca respectively, and the homology tree was constructed. The analysis of deduced amino acid sequence by molecular biology software indicated: the protein molecular weight was 29KD, isoelectric point approximately was at pH 4.8. The analysis of secondary structure of protein indicated: the protein was the mixing property protein, Alapha helix 38.6%, Beta sheets 29.5%, loop (corner) 17.3%, Coil (non-regular curl) 14.6%.(3) The genetic polymorphism of six mink breeds was investigated for MuLu-DRA gene exon 2 by PCR-SSCP, the results showed that the gene six kinds of genotypes, respectively was AA,BB,CC,AB,AC,BC. It explained that the MuLu-DRA*exon2 gene altogether was controlled by three allele A, B, C, the polymorphism is relatively low. We calculated the allele frequency, the heredity heterozygosity value(H),polymorphism information content (PIC),the heredity distance, constructed NJ cluster chart of six breeds mink, the Regal White mink first clustered with Pastel mink , then gathered JinZhou mink, the Pearl mink and Silverblue mink gathered the same group alone, finally gathered with the American mink. It explained that the Regal White mink and the Pastel mink and JinZhou mink has nearly genetic affinity, the Pastel mink and Silverblue mink had close genetic affinity. The results were consistent with mink population in our country at present, andcan respond the mink population correctly the genetic affinity. We carried on the MuLu-DRA*exon2 polymorphism and the blood target related research. The results explained that the genotype and the blood traits are non-correlated.The variety has the remarkable influence to WBC.
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