牛生长激素基因外显子5序列变异及其分子进化特征

通过双向直接测序法测定中国5个牛种生长激素(GH)基因外显子5序列,并且在分析序列变异的基础上探讨GH基因外显子5序列的分子进化特征.序列分析表明,5个牛种GH基因外显子5的遗传变异水平较低,平均核苷酸变异率约为3.48%,而且绝大多数位点的核苷酸替换是同义突变,仅发现1个错义突变位点;从GH基因外显子5序列单倍型构建的分子进化树来看,水牛与普通牛、瘤牛、牦牛及大额牛的分化相对比较明显,其他4个牛种之间并无明显分化,还享有共同的祖先序列.研究结果也说明牛GH基因外显子5在进化过程中由于功能的约束表现相当保守,进化速率缓慢.

Sequence Variations and Molecular Evolution at Exon 5 of Bovine Growth Hormone Gene

Sequences of growth hormone gene at exon 5 in five indigenous Chinese bovine species were sequenced by standard double-strand DNA sequencing method.Characters of molecular evolution were also analysed basing on sequence variations.Mutation rate at exon of GH in five bovine species was very low with the percentage of 3.48.The majority of nucleotide substitution was nonsense mutation and only one missense mutation was observed.Molecule tree based on hapiotypes of bGH at exon 5 showed that differentiation wa:apparent relatively between Bubalus bubalis and Bos taurus,Bos iruticus,Bos grunniens,Bos frontalis.There was no apparent differentiation among other four bovine species and they shared mutual ancestral sequence.Our results also demonstrated that exon 5 of bGH gene was strictly conservative under functional constraint during the course of evolution together with low evolution rate.