【作者】 张保军；

【导师】 杨公社； 孙超；

【作者基本信息】 西北农林科技大学 ， 动物遗传育种与繁殖， 2004， 硕士

【摘要】 猪的胴体瘦肉率和肉质品质是两项重要的经济性状，提高胴体瘦肉率的育种目标已取得一定进展，但肉质不断下降。我国地方猪种具有丰富的遗传多样性和优良的肉质品质，故今后的育种目标发展为以保持和合理利用我国地方猪种肉质优良的优势为前提，提高瘦肉率。而传统的育种手段很难使瘦肉率和肉质这两个呈负相关的性状同时提高，因此，随着现代分子育种技术脱颖而出，分子标记辅助选择成为一种可行的育种手段。候选基因法是研究动物数量性状遗传机制的主要方法之一，LPL基因和A-FABP基因分别被确定为影响背膘厚和肌内脂肪含量的主要候选基因。本研究选用3个国外猪种、4个中国地方猪种、1个培育品种和野猪共368头猪作为实验动物，利用PCR-RFLP技术和微卫星方法分别对脂蛋白脂酶（LPL）的第6、第8内含子和脂肪细胞型脂肪酸结合蛋白（A-FABP）基因第1内含子的微卫星序列进行了多态性分析，目的是发现新的多态性位点，为确定影响背膘厚和肌内脂肪含量的主效基因或有效的连锁标记奠定基础。主要研究结果如下：1在LPL基因第6内含子的SmaⅠ-RFLP位点上，大白猪、汉中白猪及野猪以BB型为主；长白、杜洛克和内江猪以AA和AB型为主；而荣昌猪和汉江黑猪以AB和BB型为主；基因型之间没有表现出明显的品种特征。2在LPL基因第6内含子的PvuⅡ-RFLP位点上，国外猪种均为DD纯合型，而国内猪种和野猪均存在变异；中国脂肪型猪种（除汉中白猪外）与国外瘦肉型猪种有明显的基因型差异，C等位基因可能与我国猪种高背膘厚相关。3在LPL基因第8内含子的EcoRⅠ-RFLP位点上，国外猪种和中国地方猪种均以EF基因型为主，F等位基因频率较高，没有明显的品种特征。4在LPL基因第8内含子的Hind Ⅲ-RFLP位点上，国外猪种和荣昌猪存在遗传变异，其余国内猪种和野猪均为FF纯合型。5在A-FABP基因第1内含子的微卫星位点上，共发现了16个等位基因，9种基因型。除汉中白猪没有EM基因型外，EM和GN基因型在各猪种中均有分布，且在大白猪、长白猪、杜洛克、荣昌猪和内江猪中占有优势。 <WP=7>6在A-FABP基因第1内含子的微卫星位点上，根据Chebychev遗传距离UPGMA法将8个家猪品种和1个野猪品种聚为3类：大白猪、长白猪和杜洛克为一类；荣昌猪、汉中白猪和内江猪为一类；八眉猪、野猪和汉江黑猪为一类。 7在LPL基因的4个PCR-RFLPs位点上，野猪的基因型分布、基因频率、杂合度和多态信息含量均与中国猪种一致。在A-FABP基因第1内含子的微卫星位点上，野猪的基因型分布、基因频率、遗传相似性和遗传距离也均与中国猪种相一致，说明本研究选用的野猪与中国地方猪种亲缘关系较近。更多还原

【Abstract】 Lean meat percentage of body and meat quality are two important economic characters. The meat quality is continuously declining, although the breeding aim to improve lean meat percentage of body is basically achieved. For Chinese local pig breeds are bound in genetic diversity and excellent meat quality, the breeding aim is turning into keeping and utilizing soundly the advantage of excellent meat quality of Chinese local pig breeds as well as improving lean percentage of body. It was difficult to improve both lean meat percentage of body and meat quality simultaneously through traditional breeding means because the two indexes are negatively correlative. Therefore, molecular marker assisted selection becomes a feasible breeding mean along with the emergence of modern molecular breeding technique. Candidate gene method is one of the main approaches that are often used to study genetic mechanism of quantity trait in animals. At present, LPL gene and A-FABP gene are considered to be the major candidate genes affecting back fat thickness and intramusclular fat content in porcine respectively.In this study, DNA samples from 368 pigs including 3 exotic breeds, 4 Chinese local breeds, 1 cultivated breed and Boar were analyzed. LPL gene and A-FABP gene were studied by PCR-RFLPs and microsatellite respectively. The aim of this study was to find some new polymorphic loci and then establish the foundation for determining the major genes affecting back fat thickness and intramuscular fat content or the available genetic markers linked with them tightly. The main results were as follows.1 At the SmaⅠ-RFLP locus of Intron 6 in LPL gene, BB genetype was major in Yorkshire, Haibai pig, and Boar, AA and AB genetype were major in Landrace, Duroc and Neijing pig, while AB and BB genotypes were major in Rongchang pig and Hanjing black pig. There was no character of breeds between genotypes.2 At the PvuⅡ-RFLP locus of Intron 6 in LPL gene, the exotic breeds including Large Yorkshire, Landrace, Duroc presented only DD genotype while native breeds and Boar varied. There was difference in genotypes between Chinese lardtype breeds excluding Hanzhong White pig and exotic lean breeds, and it was possible that C allele was correlative with fat deposition and high back fat thickness of native breeds. <WP=9>3 At the EcoRⅠ-RFLP locus of Intron 8 in LPL gene, EF genotype and F allele frequency were prevailing in all of the tested breeds and Boar. 4 At the Hind Ⅲ-RFLP locus of Intron 8 in LPL gene, the exotic breeds and Rongchang Pig varied while others presented only FF genotype.5 At the microsatellite locus of Intron 1 in A-FABP gene, there were 16 alleles and 9 genotypes. Expect that EM genotype existed in Hanzhong white pig, EM and GN genotypes existed in others. EM and GN prevailed in Yorkshire, Landrace, Duroc, Rongchang pig and Neijiang pig,. 6 At the microsatellite locus of Intron 1 in A-FABP gene, 8 domestic pig breeds and 1 Boar breed were divided into 3 clusters by UPGMA according to Nei’s DA genetic distance. Yorkshire, Landrace, Rongchang pig, Hanzhong white pig and Bamei pig were the first cluster, Boar and Hanjiang black pig were the second cluster, while Duroc and Neijiang pig were the third cluster.7 The genotype distribution, allele frequency, He, and PIC were identical between Boar and native breeds at 4 loci of PCR-RFLPs in LPL gene. The genotype distribution, allele frequency, genetic comparability and genetic distance were identical between Boar and native breeds at the microsatellite locus of A-FABP gene. These showed the relationship between Boar in our study and Chinese local pig breeds was close.更多还原