【作者】 刘众；

【导师】 陈玉林；

【作者基本信息】 西北农林科技大学 ， 动物遗传育种与繁殖， 2008， 硕士

【摘要】 本研究以蒙古羊、滩羊、小尾寒羊和欧拉型藏羊为研究对象,选取瘦素蛋白基因(Leptin)作为候选基因,利用6个位点对其进行遗传多样性研究,同时研究其作为候选基因对生产性状进行分子标记的可行性,得到如下结果:1.根据已公布的绵羊Leptin基因序列,分别在第三外显子,第二内含子和3’非翻译区筛选6个位点设计引物,并进行PCR扩增,均得到了特异性扩增结果。经检测L1、L2、L3和L4,4个位点存在多态性,均为三个基因型AA、AB和BB型,其中AA型为野生型,AB型为杂合子,BB型为突变基因型。L1位点BB型在404bp处有一突变,为G—A突变; L2位点BB型在103bp处有一突变,为G—T突变; L3位点BB型在162bp处有一突变,为A—G突变; L4位点BB型在268bp处有一突变,为G—A突变;4个群体在4个位点上的有效等位基因数小于实际观察等位基因数。2.本试验对4个多态位点进行基因频率卡方检验,发现L1位点只有在小尾寒羊群体处于Hardy-Weinberg平衡状态;L2和L4位点在蒙古羊和滩羊群体处于Hardy-Weinberg平衡状态;L3位点只有在欧拉羊群体处于Hardy-Weinberg不平衡状态。4个群体的平均有效等位基因数为1.7162,与实际观察值相近,说明等位基因数分布较均衡。L1、L3和L4三个位点在蒙古羊群体的多态信息含量和信息熵均大于其他3个品种群体,证明了蒙古羊具有丰富的遗传基础。L2位点在滩羊群体的多态信息含量最大,说明滩羊的该位点遗传基础丰富。3.将4个含有多态基因型的位点与4个品种绵羊的部分经济性状进行相关性分析结果如下:在蒙古羊群体中,L1位点与屠宰率存在相关性,各基因型的均值差异显著(P<0.05);L2位点与背膘厚、体重和胴体重存在相关性,但各基因型的均值差异显著(P<0.05),可作为蒙古羊活重等6个屠宰性状的标记位点,其中L2-AA型所对应活重、胴体重、背膘厚、花油重和腹脂重的最小二乘均数皆为最大,且与其他两个基因型比较,差异显著(P<0.05),可作为蒙古羊的活重等5个性状的标记基因型;L3位点只与屠宰率存在相关性,且各基因型的均值差异显著(P<0.05),对L3位点和L1位点选择效应比较得知,L3-BB基因型可作为蒙古羊群体的屠宰率标记基因型;L4位点与屠宰率存在相关性,且各基因型的均值差异显著(P<0.05)。在小尾寒羊群体中,L1位点多态性与背膘厚存在相关性,各基因型的均值差异显著(P<0.05);L3位点多态性与体重、胴体重、背膘厚、肾脏脂肪重、花油重和腹脂重存在相关性,各基因型的均值差异极显著(P<0.01),且L3-BB基因型的最小二乘均值最大,可作为胴体重、肾脏脂肪重和腹脂重的标记基因型,此外对L3位点和L4位点选择效应比较得知,L3-BB基因型也可作为小尾寒羊群体的体重和背膘厚标记基因型;L4位点多态性与小尾寒羊的体重和背膘厚存在相关性,各基因型的均值差异极显著(P<0.05)。在滩羊群体中,L3位点多态性与体重、胴体重和花油重存在相关性,且各基因型均值差异显著(P<0.05),其中L3-BB基因型对应最小二乘均值最大,可作为滩羊的体重、胴体重和花油重的标记基因型;在欧拉羊群体中,L1位点与体重有相关性,且各基因型的均值差异显著(P<0.05);L2位点与体重有相关性,且各基因型的均值差异显著(P<0.05);L3位点与体重有相关性,且各基因型的均值差异显著(P<0.05)对L3位点与L1和L2位点选择效应比较得知,L3-BB基因型也可作为欧拉羊群体的体重标记基因型。更多还原

【Abstract】 Mongolian sheep, Tan sheep, Small-Tail Han sheep and Ola Tibet sheep were used as research populations. The DNA molecular marker technologies PCR-SSCP were applied to evaluate the effects of genotypes of the candidate gene-leptin gene on carcass traits in the populations. The Association between genetic marker and the carcass traits, including the weight, carcass weight, renal adipose weight, celiac adipose weight, alvine adipose weight,dressing percentage,GR value,backfat thickness were analyzed using general linear model (GLM). The results were as follows:1.Based on the sequence of the goat leptin gene, six primers were designed, which included the exon3, intron2 and 3’UTR. The results showed that four loci were demonstrated polymorphism in the six selected locus in tested population. The genotypes were nominated AA, AB, and BB. And the AA genotype was wild type while the AB was heterozygote, the BB was mutation type.The sequencing results revealed that in the L1 locus, a G>A mutation at the 404th nucleotide; in the L2 locus, a G>T mutation was detected at the 103th nucleotide; in the L3 locus, an A>G mutation was found at the 162th nucleotide; in the L4 locus, a G>A mutation was found at the 268th nucleotide. In the tested population, the effective allele number was smaller than the observed allele number.2.The frequencies of the four loci were analyzed usedλ-test. The results revealed that at the L1 locus the Small-Tail Han sheep was at Hardy-Weinberg equilibrium; at the L2 and L4 loci the Mongolian sheep and Tan sheep were at Hardy-Weinberg equilibrium; at the L3 locus only the Ola Type Tibet sheep was at Hardy-Weinberg equilibrium. The average effective allele number was 1.7162 which was similar to the observed allele number and this implied that the distributions of the alleles were equilibrium in the four breeds. The PIC and Shannon’s information index(S) were higher in the Mongolian sheep than other breeds at the L1, L3 and L4 locus, and this suggested that the Mongolian sheep contained genetic diversity. At the L2 loci, the PIC was much higher than other breeds, it revealed that genetic diversity were ample in this locus. The association of variations of leptin gene with carcass traits in the population was analyzed. The results were showed as followe:3.In the Mongolian sheep, the genotype of the L1 locus was associated with the dressing percentage,and the relationship was significant(P<0.05); However, there was significant association between the genotype of the L2 locus and the backfat thickness、body weight and carcass weight(P<0.05), which can be used a maker of the carcass trait. The least-squares analysis showed that the body weight、carcass trait、backfat thickness、dressing percentage and celiac adipose weight of individuals , which was the L2-AA, were higher than the other which were the other two genotypes, and this suggested that the locus can be used as a maker of the traits. There was significant association between the genotype of the L3 locus and the dressing percentage(P<0.05).L3-BB can be used a maker of the carcass traits through comparing the selected effects of the L1 and L3. L4 was also associated with the dressing percentage(P<0.05). In the Small-Tail Han sheep population, there were significant relationship between the genotype of the L1 and the backfat thickness (P<0.05). and there were significant association between the genotype of the L3 and the body weight、carcass weight、backfat thickness、renal adipose weight、dressing percentage和celiac adipose weight (P<0.01). The least-squares analysis showed that the body weight、carcass weight、backfat thickness、dressing percentage andceliac adipose weight of individuals, which was the L3-BB, were the highest than the others which were the other two genotypes, and this suggested that the locus can be used as a maker of carcass weight、renal adipose weight and celiac adipose weight traits. L3-BB can be used a maker of the carcass traits through comparing the selected effects of the L3 and L4. the polymorphism of the L4 locus was also associated with the body weight and backfat thickness(P<0.05).In the Tan sheep population, there was a significant relationship between the genotype of the L3 locus and the body weight, carcass weight and dressing percentage. The least-squares analysis showed that the L3 locus can be used a maker of the body weight、carcass weight and dressing percentage.In the Ola Tibet sheep population, there was a significant relationship between the genotype of the L1 and the body weight (P<0.05), as well as the L2 and L3 (P<0.05). L3-BB can be used a maker of the body weight through comparing the selected effects of the L1 and L2.更多还原