【作者】 金丽娜；

【导师】 韩建林； 罗玉柱；

【作者基本信息】 甘肃农业大学 ， 动物遗传育种与繁殖， 2008， 硕士

【摘要】 禽类传染性疾病严重地影响着禽业生产,采用遗传改良方法提高宿主对病原的遗传抗性,开展抗病育种,是禽病防治的有效途径之一,并有益于家畜生产和人类健康。Mx蛋白和主要组织相容性复合体(MHC)因具有抗病毒作用而备受抗病育种研究者的关注。已有报道,Mx基因编码序列1892位的G/A SNP对Mx蛋白抗禽流感的功能起关键作用;应用分子标记对MHC的基因型进行测定是研究其功能的基础。本研究通过对分布于西亚、南亚和东亚的12个鸡群体378个样本的Mx基因之1892位的单核苷酸多态性的检测和对位于MHC区域内的三个微卫星标记LEI0258、MCW0371和MCW0312的遗传多态性的分析,得出以下结论:1)地方群体中Mx抗病基因型(AA)和抗病基因(A)的频率明显高于商品培育品种。地方群体中,西、南亚群体中Mx抗病基因(A)的频率明显高于中国西北和韩国(东亚)群体,其中以孟加拉(BAN)群体的抗病基因(A)频率最高(77.5﹪),中国西北会宁群体的抗病基因(A)频率最低(11.8﹪)。2) LEI0258和MCW0312基因型测定结果显示,地方群体的遗传多样性大于商业培育品种。地方群体中,西、南亚群体的遗传变异程度高于中国西北和韩国群体(东亚);其中以孟加拉(BAN)的平均多态信息含量和杂合度最高,民勤(MQ)最低。3) MCW0371序列的重复区呈Fr1(An)和Fr2((AAC)mAn)两种模式。Fr1为完全型单核苷酸重复微卫星,Fr2为有两个毗邻的重复单元的复合型微卫星。序列结构复杂,核苷酸长度相同的等位基因存在核苷酸结构不同的可能,因而难以通过片段分析对该基因座进行正确的基因型测定。另外,在其两侧翼序列中还存在多个SNPs和InDels。Fr1模式中检测到6个SNPs和4个InDel;Fr2模式中检测到16个SNPs和4个InDel。Fr2模式的多态性大于Fr1模式。更多还原

【Abstract】 Chickens and poultry industry suffer serious losses from a number of infectious diseases, some of which are fatal and all of which affect the growth, production and welfare of the birds. Selective breeding for disease-resistant chickens is considered to be the best long-term strategy in preventing the diseases, thus beneficial for both livestock industry and human health.Being identified with strong association to avian disease resistance/susceptibility, chicken Mx gene and MHC have been receiving lots of attentions from many researchers. It has been previously demonstrated that a G/A SNP at nucleotide position 1892 of coding sequence of the chicken Mx gene confers susceptibility/resistance to avian viral diseases and molecular identification of genotypes of the MHC provides a baseline for selective breeding for disease-resistant chickens.In this study, the G/A SNP at nucleotide position 1892 of coding sequence of chicken Mx gene was examined using mismatched primer PCR-RFLP and the genetic polymorphisms at three microsatellite loci namly LEI0258, MCW0312 and MCW0371 located within the MHC region were assessed in 378 chickens from 12 populations collected in West, South and South-East Asia. Some results are as follows:1) Frequencies of resistant genotype AA and allele A in indigenous chickens were higher than those in commercial ones. Allele A in indigenous birds from West Asian and South Asian were more than those from northwestern China and Korea.2) The genetic polymorphisms at the LEI0258 and MCW0312 loci in indigenous populations were more diverse than those in commercial breeds in terms of NA, PIC and H. Genetic variations of West and South Asian indigenous chickens were higher than those of northwestern of China and Korea.3) There were two different structures in sequences of the MCW0371 locus that was previously reported to have exclusively a single nucleotide repeat. One structure consisted of two un-interrupted repeat elements, a 3 bp repeat of“AAC”ranging between 1 and 6 followed by a single nucleotide repeat of“A”between 9 and 17 (Fr2); the other only had the single nucleotide repeat of“A”between 14 and 20 (Fr1). Therefore it is impossible to accurately genotype this locus due to its complex structure. Furthermore, 16 SNPs and 4 InDels were detected in the Fr2, and 6 SNP and 4 InDels in the Fr1 within the franking sequences of this locus.更多还原