| 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... |
