【摘要】 3头扬子鳄血样取自宣城安徽省扬子鳄繁殖研究中心。利用一对简并引物对MHCⅡ类B基因第二外元的部分片段进行扩增 ;通过克隆、单链构象多态性分析、测序 ,并将测得序列与下载的 8个物种MHC序列比对 ,确定序列差异和变异位点 ;利用MEGA软件构建NJ树 ,PAUP4 0构建MP树。结果得到 10种不同的序列 ,片段长 16 6bp。核苷酸序列中有 38个变异位点 ,氨基酸序列中有 2 3个变异位点 ;推定的抗原结合位点非同义替换 (dN)明显高于同义替换 (dS)。 10种序列的NJ树和MP树极为相似 ,均为A、B两个分支 ,两个分支明显的特异性位点核苷酸序列中有 9个 ,氨基酸序列中有 7个。表明扬子鳄MHCⅡ类B基因第二外元有较高的多态性 ,有利于扬子鳄饲养种群的遗传保护。更多还原

【Abstract】 A pair of degenerate primers were used to amplify polymorphic segments of the second exon of MHC class Ⅱ B genes from the genomic DNA of Alligator sinensis.Sequences were obtained from cloning,single strand conformation polymorphism analysis and sequencing.By comparing with another eight species MHC sequences,differences from sequences and variable sites were confirmed.Phylogenetic relationships were constructed by neighbor-joining method in MEGA and maximum parsimony method in PAUP4.0.Ten different nucleotide sequences were obtained,which were 166 bp long (except one 160 bp).There are 38 variable sites among ten nucleotide sequences and 23 variable sites among amino acid sequences.The number of nonsynonymous (d N) substitutions of pABS was higher than that of synonymous (d S) substitutions.The ten nucleotide sequences can be clustered into two clades (group A and B) in NJ and MP phylogenetic trees.Some specific sites were found between the two groups,including 9 nucleotide sites and 7 amino acid sites.The high polymorphism of MHC class Ⅱ B genes in A.sinensis was of great benefit to genetic conservation in the captive population of A.sinensis.更多还原