【作者】 苏锐；

【导师】 雷初朝；

【作者基本信息】 西北农林科技大学 ， 遗传学， 2008， 硕士

【摘要】 为了研究中国家马的遗传多样性与起源进化,本研究利用PCR技术和生物信息学技术对我国9个家马品种(宁强马、哈萨克马、贵州马、关中马、蒙古马、西藏马、关山马、云南马和广西马)182个个体的线粒体DNA(mtDNA) D-loop 247bp序列进行分析,得到如下主要结论:(1)在所分析的9个家马品种182条序列中,D-loop区T、C、A、G 4种核苷酸的平均比例分别为29.7%、26.6%、31.8%、11.9%。A+T含量为61.5%,G+C含量为38.5%,A+T含量明显高于G+C含量,符合哺乳动物线粒体DNA碱基组成的基本比例。(2)9个家马品种182条序列中,检测到70种单倍型,47个核苷酸多态位点,约占所测核苷酸长度的19.03%,其中有43个转换,2个颠换,2个转换与颠换共存。(3)9个家马品种单倍型多样度和核苷酸多样度在各品种中的分布分别为0.842~0.994和0.0219~0.0293,均以关中马最小,蒙古马最大,平均单倍型多样度和核苷酸多样度分别为0.946和0.0247,表明中国家马具有丰富的遗传多样性。(4)mtDNA D-loop序列的NJ系统发育树表明,中国家马分为A-G 7个支系17个亚支系,表明为多母系起源。(5)引用了9条中国古代马的D-loop序列,对这9条序列和中国家马的70种单倍型构建NJ系统发育树,结果发现中国古代马与现代家马有相似的mtDNA支系,9条序列形成了7个单倍型,分别聚到A,E和F支系中;这个结果也指出史前时期蒙古草原的马群体可能是多起源的,经过对家马和古马DNA序列比对,支持当前所普遍接受的家马多起源学说。更多还原

【Abstract】 All 182 mtDNA D-loop 247bp sequences of 9 Chinese domestic horse breeds were analyzed to detect their genetic diversity and origin by using PCR and bioinformation technology. These horse breeds includes Ningqiang horse, Kazak horse, Guizhou horse, Guanzhong horse, Mongolia horse, Tibet horse, Guanshan horse, Yunnan horse and Guangxi horse. The main results in this study are as follows:(1) Among all 182 sequences of 9 domestic horse breeds,the average nucleotide content are: 29.7% for T, 26.6% for C, 31.8% for A and 11.9% for G. Average (A+T) content is 61.5% and 38.5% for (G+C), the former is apparently higher than the latter, it is suggesting that the base bias which is in proportion to mammalian mitochondrial DNA nucleotide composition.(2) All 182 sequences defined 70 different haplotypes with 47 variable sites. 47 sites are with 19.03% of 247 bp D-loop region, 43 of these sites are transitions, 2 of them are transvertions, 2 of these sites have both transitions and transvertions.(3) There is high level of genetic diversity in Chinese domestic horses. The haplotype diversity and the nucleotide diversity were 0.842~0.994 and 0.0219~0.0293 respectively, of which Guanzhong horse displayed the lowest level, while Mongolia horse held the highest. The mean haplotype diversity and the mean nucleotide diversity in all breeds were 0.946 and 0.0247.(4) NJ phylogenetic analysis in Chinese horse mtDNA suggested that Chinese domestic horse revealed seven maternal origins (A-G), 17 sublineages,showing multiple maternal origins.(5) Nine ancient DNA sequences were compared with 70 haplotypes from Chinese native horses. The NJ tree showed that the 9 ancient DNA sequences shared 7 haplotypes which were quite similar to modern day equine mtDNA, clustered in haplogroups A, E, and F. This result also suggested that horses of prehistoric Mongolian plateau probably had multiple origins. The modern and ancient mtDNA sequences presented here support the currently accepted hypothesis of multiple origins in horses.更多还原