本研究利用已公布的4165个来自于全世界196个品种的山羊线粒体D_Loop序列，进行核苷酸多样性、单倍型构建、单倍型多样性、群体系统发育学研究、中性检验及群体遗传距离等一系列遗传参数进行评估。在全部个体的401 bp片段长度的D_Loop区域内共鉴定得到301个多态位点，总体核苷酸多样性为0.03471；构建获得并构建2409个D_Loop单倍型，单倍型平均多样性为0.9983。系统发育分析表明，98.92%的单倍型被聚类为已知的6个山羊线粒体D_loop单倍型簇，其中单倍型A所占比例最大(86%)，D_Loop单倍型B簇在中国山羊中出现频率最高。中国西南地区山羊群体中发现了两个未知的D_Loop单倍型簇(Unknown I和Unknown II)。分子方差分析(AMOVA)和群体间成对差异(PiXY)研究结果表明，不同品种家养山羊间群体变异较小，群体遗传分化与地理分布不完全一致，表明群体间广泛存在遗传物质交流。中性检验(Tajima‘D和Fu’Fs检验)和错配分布研究结果表明，单倍型簇B、C和G存在群体扩张历史。较其他野羊，Capra aegagrus与家养山羊系统发育关系最为密切，并可能贡献于山羊A、B、C和F单倍群簇的驯化起源。本研究表明线粒体D_Loop单倍型B簇可能起源于中国或在山羊驯化早期已迁至中国，在中国西南地区山羊群体中两个未知的D_Loop单倍型簇的发现表明中国西南地区可能具有独特的山羊母系背景或驯化历史；Capra aegagrus是最可能的家养山羊野生祖先，并可能贡献于山羊A、B、C和F单倍群簇的驯化起源。本研究利用大样本量全世界山羊线粒体D_Loop序列数据集分析有助于更好的理解世界范围内山羊母系驯化起源及基因流动的历史变化，为进一步明确世界山羊群体迁徙的演变历史及种群系统发育定位提供了宝贵的理论依据。

In the present study we studied the genetic structure of five Chinese sheep populations of Hu sheep, Tong sheep, SmalltailedHan sheep, Tan sheep, and Wadi (WD) sheep using 15 microsatellite loci. The results showed that the FIT, FST, andFIS statistics computed for the complete dataset had the following values, 0.523±0.140, 0.363±0.131 and 0.263±0.092,respectively. All loci were significantly contributed to the genetic differentiation among population (P<0.001). There is norelationship between the scatter of pairwise FST geographical distance points as geographical distance increases betweenthe five populations. Membership probabilities and genetic structure of sheep populations were estimated when K=2, thepopulations were classified into Hu, Tong, Han and WD, and Tan sheep group. However, when K=3, the populations wereclassified into Hu and Tong, Han and WD, and Tan sheep group. The findings supported the previous literatures thatthese populations are originated on different time stages from the primogenitor population and communicated geneticallywith each other by natural and artificial selection in different ecological environment.

Research on the identity of genes and their relationship with traits of economic importance in farm animals could assist in the selection of livestock. In this study, the polymorphisms of insulin-like growth factor 1 (IGF1) gene in 561 goats of ten breeds were detected by polymerase chain reaction (PCR)-single strand conformation polymorphism (SSCP) and their association with litter size and birth weight in three breeds were investigated. The effects of IGF1 polymorphisms on the breeding value for litter size and birth weight were examined using least square methods. Two deletions (CA) were detected in the microsatellite and two mutations (A1637G, T1640C) were found in 5´-flanking regulatory region. No significant association between the polymorphisms in 5´-flanking region of IGF1 and birth weight was found in the three breeds of goats. In Gulin Ma goats, two polymorphisms were found to affect litter size traits. In Chuandong White goats and Guizhou White goats, no significant difference (P<0.05) in litter size between goats carrying different genotypes was observed. Further evaluation and confirmation studies in more goat populations with larger sample sizes are necessary.