2种三疣梭子蟹居群线粒体Cyt b和S-rRNA基因片段序列变异研究

目的：通过对2种三疣梭子蟹居群样线粒体C弘b和S-rRNA基因片段的序列分析，探讨其遗传变异，为种质资源的管理、保存和利用提供依据．方法：采集山东潍坊和福建厦门两个不同居群的三疣梭子蟹样，提取其线粒体DNA．由Genebank获得三疣梭子蟹完整线粒体DNA序列（登陆号：NC_005037），设计扩增Cyt b和S-rRNA基因片段引物，经PCR扩增获得预期产物，纯化后测序．结果：以提取的线粒体DNA为模板扩增出特异性强的Cyt b和S-rRNA基因片段，与预期条带长度429bp和465bp吻合；2个基因片段的AT含量均高于GC含量；Cyt b基因片段有3个位点发生了突变，S-rRNA只有1个位点发生了突变；在两种居群的4个突变位点中，2个位置突变为相同的碱基，且所有突变位点均呈转换方式．结论：Cyt b基因序列比S-rRNA基因序列具有相对高的突变率；研究的2个基因片段的突变位点的碱基置换主要呈转换方式；来自2个三疣梭子蟹居群样本的线粒体S-rRNA基因的突变发生在同一位点且突变为相同碱基，表明2个居群具有较近的亲缘关系．

Sequence Variations of Mitchondrial Cyt b and S - rRNA Gene Fragments in Two Chinese Portunus trituberculatus Populations

Purpose ： Genetic variations of mitochondrial Cyt b and S-rRNA gene fragments of two Chinese Portunus trituberculatus populations are analyzed in order to accumlate basic information for management, protection and utilization of the economically important marine species. Methods ： Primers for amplifing the fragments of mitchondrial Cyt b and S-rRNA genes are designed accordring to Genebank（ ACCESSION： NC_005037 ）. Extraction of mtDNA from Weifang and Xiamen Portunus trituberculatus populations are done with high salt- concentration-precipitation method, PCR products are obtained and sequenced with ABI PRISM 3730. Final- ly, sequence alignment of the 2 genes are done by DNAMNA6. 0. 40. Results ： Mitchondrial DNA of Portunus trituberculatus is successfully extracted, specific bands of 429 bp for Cyt b and 465 bp for S-rRNA are amplified by PCR, which is consistent with the predicted lengths. The content of A and T is obviously higher than that of G and C in the two gene fragments; 3 mutantion sites are found in Cyt b gene fragments but only one found in S-rRNA ; 2 out of the 4 sites mutate into a common base between Weifang and Xiamen samples, all of the 4 sites belong to transition type. Conclusion： There are higher mutation rate for Cyt b gene than for S- rRNA gene, point mutantion of the 2 genes mostly occur in the type of transition. There exsits a close genetic relationship between the two Chinese Portunus trituberculatus populations.