【作者】 朱砺；

【导师】 李学伟；

【作者基本信息】 四川农业大学 ， 动物遗传育种与繁殖， 2004， 博士

【摘要】 一 MRFs基因家族内各基因的PCR-RFLP遗传多态性及其遗传效应 以7个地方品种、2个外种猪品种、1个培育品种和2个杂交猪群体共12个群体202头个体作为材料，对MRFs基因家族各基因的PCR—RFLP(MyoG／Msp Ⅰ、Myf-5／Hinf Ⅰ、Myf-6／Ava Ⅰ和MyoD／Dde Ⅰ)遗传多态性及其遗传效应进行了系统的研究。结果表明： MyoG基因：3’端Msp Ⅰ酶切的M等位位点是中国地方猪种中的优势位点，N等位位点仅以杂合子的形式存在于地方猪种群体。从遗传效应来看，N等位位点能极显著地使肌纤维变粗，肌纤维面积变大，增加胴体瘦肉率和眼肌面积，降低皮脂含量(P＜0.01)，改善胴体产肉量和提高胴体品质，对FOM肉脂仪测定的胴体性状影响不显著(P＞0.05)；能极显著地降低猪肉品质，使pH值、肉色和肌内脂肪含量降低，并使肌肉的系水力变差(P＜0.01)；使饱和脂肪酸C14：0的含量显著降低(P＜0.05)，对氨基酸组成的影响不显著。具体讲，其N等位位点对增加肌纤维面积的加性效应值和显性效应值分别为896.14μm~2和174.85μm~2；对增加胴体瘦肉率的加性效应值和显性效应值分别为3.929％和-0.602％；对增加眼肌面积的加性效应值和显性效应值分别为2.0985cm~2和-0.5775cm~2；对皮脂率的加性效应值为-3.0245％，显性效应值为-0.4045％。N等位位点对pH1的加性效应值和显性效应值分别为-0.167和0.034；对贮藏损失的加性效应值和显性效应值分别为0.558和-0.347；对肌内脂肪含量的加性效应值和显性效应值分别为-0.963和-0.217。 Myf-5基因：内含子1内的Hinf Ⅰ酶切位点多态性不丰富。A等位位点在中国地方猪种中具有绝对优势，B等位位点主要存在于除中国地方猪种以外的引进品种以及含引进品种血缘的培育品种和杂交品种中，且频率较低。就遗传效应而言，虽然没有BB纯合个体的出现，但其AB杂合个体肌纤维的直径(79.281μm，78.644μm)极显著地大于AA纯合个体的肌纤维直径(71.196μm，70.593μm)；AB杂合个体的肌纤维面积(4346.210μm~2)显著地大于AA纯合个体的肌纤维面积(3602.900μm~2)。表明B等位位点具有极显著的使肌纤维变粗和面积变大的遗传效应(P＜0.01)；极显著地增加FOM肉脂仪测定的胴体瘦肉率(P＜0.01)，显著降低胴体背膘厚度，提高FOM测定的胴体等级(P＜0.05)；显著降低肌内脂肪含量和24小时肉色评分(P＜0.05)。对脂肪酸和氨基酸的组成影响不显著。 Myf-6基因：内含子1内的Ava Ⅰ酶切位点多态性不丰富，在多数中国地方猪种中A等位位点已经完全固定。就遗传效应而言，尽管没有检测到BB纯合个体，但AB杂合个体的瘦肉率为50.344%，极显著地高于AA纯合个体(45.875%)。AB杂合个体的眼肌面积为27.097cm2，极显著地大于AA纯合子个体(22.572cm2)，表明B等位位点具有极显著的增加胭体瘦肉率的遗传效应(P<0.01):AB杂合个体的皮脂率(39.889%)极显著地低于AA纯合个体的皮脂率(44.503%)，表明B等位位点具有极显著地降低皮脂含量的遗传效应 (P<0.OI)。此外，Myf-6基因对各肌纤维生长性状、FoM肉脂仪测定的胭体性状、肉质性状以及氨基酸和脂肪酸的组成等都没有显著影响。 MyoD基因:内含子1内的Ddel酶切位点多态性较丰富。在多数地方猪种群体中，C等位基因的分布具有绝对的优势，且主要以杂合子形式存在。突变型A等位位点对胭体性状的影响最大，可极显著地增加胭体瘦肉率和眼肌面积，降低皮脂含量，提高腿臀比例，增加恫体长度(P<0 .01);同时会降低猪肉品质，显著降低肌肉中的苏氨酸(Thr)、精氨酸(Arg)、酪氨酸(Tyr)、亮氨酸(Leu)和苯丙氨酸(Phe)的含量(P<0.05);显著增加肌肉中不饱和脂肪酸(C15:l和C18:3)的含量，同时显著降低饱和脂肪酸C16:O的含量(P<0.05)，使脂肪的质地变松软。具体讲，其A等位位点对增加肌纤维面积的加性效应值和显性效应值分别为457.915 0 mZ和431.055om2;对增加胭体瘦肉率的加性效应值和显性效应值分别为3.5940，0和一0.1530，0;对增加眼肌面积的加性效应值和显性效应值分别为3.084em2和一o.46emZ;对皮脂率的加性效应值和显性效应值分别为一3.9155%和0.6655%;对提高腿臀比的加性效应值为0.771%，显性效应值为0.068%。A等位位点对屠宰后45分钟和冷藏24小时后的肉色评分的加性效应值分别为一0.1445和一0.16，显性效应值分别为一0.0515和一0.213。 二MyoG基因的序列多态性及其分子进化分析 选用雅南猪、荣昌猪、成华猪、内江猪和大河猪等5个西南型猪种和高原型的藏猪、华南型的五指山猪和江海型的太湖猪共8个地方品种;1个外种猪杜洛克;以及1个培育品种大河乌猪共11个品种63头个体作为实验材料。测定包含3个外显子和2个内含子以及大部分5’侧翼区的共计26O5bp的MyoG基因全序列，以分析MyoG基因的序列多态性及其分子进化机制。结果表明: 1 MyoG基因全序列中C十G碱基的含量显著高于A十T碱基的含量。导致全序列中G十C碱基含量偏高的主要原因在于编码区内存在极高的G、C碱基含量，而编码区内的G、C碱基又主要集中分布在密码子的第三位碱基和第一位碱基，尤其是第三位。这种碱基组成的偏差有利于维持编码区结构的稳定。 2总体上看，MyoG基因更多还原

【Abstract】 1. The PCR-RFLP Polymorphisms of MRFs Gene Family and Their Genetic EffectsA total of 202 finishing pigs, including 7 native breeds, 2 foreign breeds, 1 developed breed and 2 hybrid breeds were used in this experiment to study the PCR-RFLP polymorphisms of MRFs gene family and their genetic effects. From the experiment, we can get the following conclusions.Myogenin gene (MyoG). MyoG/MspJ polymorphism (3’ noncoding region) was analyzed in the experiment. M allele is the dominant allele exists in Chinese native pig breeds; N allele only exists in the form of heterozygotes in native breeds. The N allele has significant genetic effects of improving the size of muscle fiber, carcass lean percent and the loin eye area, decrease the fat content (P<0.05), but no significant influence was found to the FOM carcass traits (P>0.05). As meat quality traits be considered, the N allele will highly significantly decrease the pH value, meat color, intramuscular fat content and increase the drip loss (P<0.01) and will cause the worse of meat quality. The N allele will also significantly decrease the content of C14:0 (P0.05), but has no significant effect to the composition of amino acid (P>0.05). When consider of the genetic values of different traits, the N allele with additive effects of 896.14um2 to the size of muscle fiber, 3.929% to carcass lean percent, 2.0985cm2 to loin eye area, -3.0245% to the fat content, -0.167 to the pHl value, 0.558% to the drip loss and -0.963% to intramuscular fat content.Myf-5 gene. Myf-5/Hinfl genotypes (intron 1) were observed, but the polymorphisms of that site were not abundant. A allele is the dominant allele exists in Chinese native breeds; B allele only exists with very low frequency in foreign breed, developed breed and hybrid breed but not be found in Chinese native breed. Although no BB individuals are found in the experiment, the muscle fiber diameter of AB individuals (79.281um, 78.644um) is highly significantly bigger than that of AA individuals (71.196um, 70.593um) (P<0.01), the muscle fiber size of AB individuals (4346.21 Own2) is significantly larger than that of AA individuals (3602.900 um2)(P<0.05). That means the B allele can significantly increase the size of muscle fiber. B allele can also significantly increase FOM carcass lean percent and decrease the fat thickness (PO.05). But the B allele has negative effect to meat quality traits, which will significantly decrease intramuscular fat contentand meat color score (P<0.05). No relationship between specific haplotype with the composition of fatty acid and amino acid was established.Myf-6 gene. The polymorphisms of Myf-6/AvaI genotypes (intronl) were not abundant. All of Chinese native pigs are AA homozygotes. B allele can be found only in foreign pig breeds and hybrid pigs. Although no BB individuals are found in the experiment, the carcass lean percent of AB individuals (50.344%) is highly significantly higher than that of AA individuals (45.875%) (P0.01), the loin eye area of AB individuals (27.097 cm2) is highly significantly larger than that of AA individuals (22.572 cm2)(P<0.05). That means that the B allele can very significantly increase carcass lean percent and loin eye area, and decrease the carcass fat content. No significant genetic effects of the genotypes were found to the muscle fiber, FOM carcass traits, meat quality and the composition of fatty acid and amino acid.MyoD gene. The polymorphisms of MyoD/Ddel gene (intronl) are abundant. C allele is the dominant allele exists in Chinese native pig breeds and mainly exists in the form of AC heterozygotes. The mutation allele A has significant positive effects to carcass quality traits, which can highly increase the carcass lean percent and loin eye area, decrease fat content, increase carcass length and the ham percent. Negative relationship between A allele and meat quality trait also be found: the A allele can significantly decrease the content of Thr, Arg, Tyr, Leu and Phe; and can significantly increase the content of C15:l and C18:3, but the content of更多还原