【作者】 吐尔孙江·努尔麦麦提；

【导师】 马合木提·哈力克；

【作者基本信息】 新疆大学 ， 动物学， 2009， 硕士

【摘要】 目的:探讨MHC-DRB3基因在和田羊和塔什库尔干羊新疆两个地方绵羊群体中的多态性,并初步判断这两个绵羊品种的遗传多样性和亲缘关系,为今后绵羊的抗病标记辅助选择奠定基础,以培育出抗病力强的绵羊品种。方法:应用直接测序(direct sequencing, DR)技术检测和田羊和塔什库尔干羊两个新疆地方绵羊品种73只个体MHC-DRB3基因的序列多态性;根据测定的基因序列,通过统计分析软件得出遗传多态性、遗传多样性参数值,并计算出两个绵羊品种的遗传距离并构建系统发育树。结果:(1)共检测出493个突变位点、279个多态位点。其中和田羊的41个MHC-DRB3基因序列的T、C、A、G 4种碱基比例分别为19.6%、25.9%、21.8%和32.6%;GC的比例为58.5%;突变位点为290,多态位点为153。塔什库尔干羊的32个序列中T、C、A、G 4种碱基比例分别为16.5%、23.9%、22.5%和37.1%;GC的比例为61%;突变位点为203,多态位点为126。(2)共发现73个单倍型。其中和田羊中发现的单倍型数为41,单倍型多样性为(HD)1.00;核苷酸多样性(Pi)为0.33322;平均核苷酸差异(K)为52.316%。塔什库尔干羊中发现的单倍型数为32,单倍型多样性(HD)为1.00;核苷酸多样性(Pi)为0.11857;平均核苷酸差异(K)为25.137%。(3)基于MHC-DRB3基因序列计算出来的两个绵羊品种的平均遗传距离为0.058;基于两个绵羊73个MHC-DRB3基因序列构建的系统发育树中,大部分和田羊个体分布于一大分枝上,而大多数塔什库尔干羊个体分布于另一大分枝上;只有很少数一部分不同品种的个体混合分布于同一分枝上。结论:MHC-DRB3基因在和田羊和塔什库尔干羊群体中的多态性均非常高;根据MHC-DRB3基因序列得到的遗传多样性参数值和遗传距离表明,和田羊和塔什库尔干羊群体都具有丰富的遗传多样性,和田羊群体的遗传多样性高于塔什库尔干羊群体的遗传多样性;并两个绵羊品种的亲缘关系为很接近。本试验结果来看,绵羊MHC-DRB3基因在品种间具有明显的序列差异,因而可作为一个品种水平上的可靠的遗传标记。更多还原

【Abstract】 Objective: This study mainly discusses the polymorphisms of MHC DRB3 gene in Hotan sheep and Tashkorghan sheep which are two of the native sheep breeds in Xinjiang , and fundamental studies were also carried out on the genetic diversity of these sheep breeds and phylogenetic relationship between them aiming at providing a strong base for the future studies of disease resistance marker-assisted selection and genetic breeding purposes. Methods: Seventy-three individuals of sheep belonging to two different native breeds in Xinjiang were studied for polymorphisms in MHC DRB3 exon2 using direct sequencing(DR) method; Population genetics statistical softwares were used to evaluate the genetic diversity of these sheep populations and to measure the genetic distances between them based on the acquired MHC DRB3 gene sequence. Results: (1) 493 mutation sites and 279 polymorphic sites were found altogether. In 41 Hotan sheep sequences, The base ratio of T, C, A, G were 19.6%, 25.9%, 21.8%, 32.6% respectively; the proportion of GC base was 58.5%; and the mutation sites were 290, the polymorphic sites were 153. In 32 Tashkorghan sheep sequences, the base ratio of T, C, A, G were 16.5%, 23.9%, 22.5%, 37.1% respectively; the proportion of GC base was 61.0%; mutation sites were 203 and the polymorphic sites were 126. (2) 73 haplotypes were found altogether. The number of haplotypes in Hotan sheep sequences was 41, the haplotype diversity(HD) was 1.00; the nucleotide diversity(Pi) was 0.33322; the mean nucleotide differences(K) was 52.316%. The number of haplotypes in Tashkorghan sheep were 32, the haplotype diversity(HD) was 1.00; the nucleotide diversity(Pi) was 0.11857; the mean nucleotide differences(K) was 25.137%. (3) The mean genetic distance based on the MHC DRB3 gene sequences of two populations was 0.058; The phylogenetic tree of 73 individuals from two sheep poplulations were constructed based on the MHC DRB3 gene sequences, on which, most of the Hotan sheep sequences distributed on the same branch of the tree, and most of the Tashkorghan sheep sequences distributed on the another branch of the tree; seldom sequences from different breeds distributed on the same branch. Conclusion: MHC DRB3 gene shows high polymorphisms both in Hotan sheep and Tashkorghan sheep populations; the genetic diversity parameters and genetic distance obtained from the MHC DRB3 sequence indicates that both breeds invoved have very rich genetic diversity and the genetic diversity of Hotan population was higher than that of Tashkorghan population; the phylogenetic relationship between Hotan and Tashkorghan breeds were very close. It can be concluded from the phylogenetic tree of two sheep breeds that there are obvious distinction in MHC DRB3 gene sequences between different breeds, which further indicates the possibility of MHC DRB3 being a genetic marker on the breed level.更多还原