| 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. |
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