河西绒山羊DRB3基因外显子2多态性分析

Polymorphism of the DRB3 Gene Exon 2 in Hexi Cashmere Goats

研究采用PCR-SSCP方法检测1 046只河西绒山羊DRB3基因第2外显子的多态性,并克隆、测序群体内变异产生的各等位基因,分析各等位基因间的遗传关系和进化意义。结果表明,河西绒山羊DRB3基因第2外显子表现了18个等位基因(LG001-LG018)控制的31个基因型,LG005为优势等位基因,LG005*005为优势基因型,18个单倍型序列分析发现44个核苷酸多态位点、29个氨基酸多态位点;与GenBank下载序列比对分析结果表明,16个DRB3的等位基因是本研究首次发现;DRB3基因遗传多态指数中,观察杂合度为0.269 6,多态信息含量为0.869 9,有效等位基因数为1.369 1;经χ2适合性检验,该群体偏离了Hardy-Weinberg平衡状态(P<0.05);18个DRB3基因外显子2的单倍型序列NJ系统发育树呈2支分化趋势。研究认为河西绒山羊DRB3基因第2外显子具有丰富的遗传多态性;河西绒山羊DRB3基因最初由2个等位基因突变分化成两大类等位基因。

Variation in the 1 046 cashmere goats DRB3 gene extron 2 was investigated by PCR-SSCP method, followed by cloning and DNA sequencing, then analysis the genetic relationship and evolutionary significance of the alleles. The results showed that there were 31 genotypes, included 18 alleles （ LGOO1-LGO18 ） . Allele LG005 and genotype LGO05＊O05 were predominant. 44 nucleotide polymorphism sites or 29 amino acids polymorphic locis were identified in 18 DRB3 gene haplotypes. 16 novel DRB3 exon 2 alleles were found comparison with GenBank sequences. In the genetic polymorphism parameters of DRB3 gene, the searched heterozygosity were 0.269 6, polymorphism information content were 0.869 9 and the effective number of alleles were 1.369 1. Chi-square test indicated that the polymorphic locus in cashmere goats were out of Hardy-Weinberg equilibrium （ P〈0.05 ） . The phylogenetic tree results showed that the 18 haplotypes of DRB3 gene exon 2 can divide into two clusters. It is showed that cashmere goats DRB3 gene exon 2 has high level of sequence polymorphism, cashmere goats DRB3 gene were differentiated into two major categories alleles from 2 mutant alleles at first.