甘肃河西地区西门塔尔杂交类群NGB基因第3外显子的遗传变异研究

摘要

This study was designed to systematically analyze the genetic polymorphism and variability of NGB gene exon 3 of 283 Simmental cattle hybrid taxon in Gansu Linze, Ganzhou, Wuwei, Jinchang, and Gaotai. DNA fragment containing the exon 3 and part of intron of NGB gene was amplified and genotyped using PCR single-strand conformational polymorphism(SSCP)method. Representative alleles were sequenced for verification of their variations in DNA sequences. The results displayed that there were 5 alleles(A, B, C, D and E) detected, combined five genotypes as AA, AB, AC, AD and AE. Among them, samples from Ganzhou, Wuwei and Jinchang were detected AA and AB genotypes, AA and AE genotypes in Gaotai and AA, AB, AC and AD genotypes in Linze. Allele A was the predominant allele and AA was the predominant genotype in five breeds. Sequence of the SSCP showed 6 mutations in the DNA fragment(75 bp C→T, 78 bp C→G, 128 bp G→A, 214 bp G→A, 232 bp C→T, and 233 bp G→A). In which, C→T at 75 bp and C→G at 78 bp were located in intron, while the other mutations were located in exon. G → A mutation at 214 bp, C → T mutation at 232 bp and G → A mutation at 233 bp were lead to Gly→Ser, Arg→Trp and Arg→Gln, respectively. Chi-square testing indicated the three gene mutation were all in Hardy-Weinberg equilibrium(P>0.05). Population genetics analysis showed the polymorphism information content were 0.0582, 0.0196, 0.0196, 0.0161 and 0.0159 in Linze, Ganzhou, Wuwei, Jinchang, Gaotai, respectively, which was at low polymorphism(PIC<0.25).%旨在对甘肃河西的临泽、甘州、武威、金昌、高台5个地区283头西门塔尔杂交类群NGB基因第3外显子的遗传多态性及变异特征进行系统分析，采用PCR-SSCP方法检测了283头西门塔尔杂交类群NGB基因第3外显子和部分内含子的多态性，且对群体内各等位基因进行了测序。结果显示，5个地区西门塔尔杂交类群共检测出5个等位基因（A、B、C、D、E），表现为5种基因型（AA、AB、AC、AD、AE）。其中甘州、武威、金昌西门塔尔杂交类群NGB基因均只检测到AA、AB 2种基因型，高台西门塔尔杂交类群检测到AA、AE 2种基因型，临泽西门塔尔杂交类群检测到AA、AB、AC、AD 4种基因型。A等位基因和AA基因型的频率在5个群体中最高，为优势基因和优势基因型。对不同SSCP带型的对应片段进行测序分析，共发现6个核苷酸突变位点（75 bp C→T，78 bp C→G，128 bp G→A，214 bp G→A，232 bp C→T，233 bp G→A），其中第75 bp和第78 bp处的突变位点位于内含子区域，其余4处突变位点均位于外显子区域。第214 bp处的核苷酸突变导致甘氨酸（Gly）突变为丝氨酸（Ser），第232 bp处核苷酸突变导致精氨酸（Arg）突变为色氨酸（Trp），第233 bp处核苷酸突变导致精氨酸（Arg）突变为谷氨酰胺（Gln），经χ2检验结果显示，5个地区的西门塔尔杂交类群在此3个突变位点上都处于Hardy-Weinberg平衡状态（P>0.05）。群体遗传学分析结果表明，临泽、甘州、武威、金昌、高台西门塔尔杂交类群的多态信息含量（PIC）分别为0.0582、0.0196、0.0196、0.0161、0.0159，均属于低度多态（PIC<0.25）。