Cloning, SNPs Detection Of RXRG And MyoD1 Genes And Association Analysis Between Polymorphism And Meat Quality And Twinning Traits In Beef Cattle

514 blood samples from 4 cattle populations-Qinchuan, Luxi, Simmental, and Angus were collected to extract genomic DNA, and some tissues samples from Simmental were taken to extract total RNA in this study. Then the isolation, identification and biologic information sequence analysis to the bovine RXRG gene and MyoD1 gene for the cDNA sequence and genomic sequence was performed by homology cloning and bioinformatics approach combined with electronic-PCR technique, RT-PCR and PCR-RFLP. And then, SNPs within some genomic fragments of the two gene were detected by sequencing. Finally, the association between RXRG and MyoD1 gene with some bovine twinning trait and meat quality traits in 6 populations were investigated. The main results were as follows:1. Bovine RXRG gene cDNA by RT-PCR, the product was cloned in PMD19-T vector. The sequencing result showed that the fragment sequence coincided with the prediction, which is 1811 bp long. The analysis of amino acid sequence indicated that cattle RXRG gene consisted 10 exons and coded 463 amino acids. Homologous comparison with some animals indicated that cattle RXRG cDNA shared 89.5%, 93.4%, 87.2%, 83.9%, 85.2% similarity in nucleic acid sequence with human, pig, macaca, mouse and rattus. The cDNA of RXRG gene was cloned. RXRG cDNA was found in muscle tissue by the analysis of its expression in various tissues, but didn't be found in other tissues.2. A new SNP of cattle RXRG gene A1941G was detected by sequencing at 3′UTR. Different genotypes were determined in Luxi monotocous cows, Luxi twinning cows, Simmental cows, Angus cows and Simmental×Mongolia cows by restriction fragment length polymorphism (PCR-RFLP). The value of polymorphism information content indicated that this was a moderate polymorphism in Luxi monotocous cows and Luxi twinning cows. Theχ2 test indicated that the polymorphic locus in Luxi twinning cows did not fit Hardy-Weinberg equilibrium (P<0.05). Theχ2 test of associational analysis between genotypic distribution and twinning or monotocous trait in Luxi cows showed that the difference was very significant (P<0.01).3. Based on gene pooling and sequencing, a new SNPs was found on the bovine MyoD1 gene, its transition C-T leads to a reaplacement of glicine with serine. Polymorphism and relationship with the carcass traits was analysised by PCR-RFLP in different populations. The transition of this locus fit in with Hardy-Weinberg equilibrium in Simmental cattle and Luxi cattle, but not in Qinchuan cattle. Statistical analysis revealed higher value in back fat and thickness of thigh (P<0.05), not in average daily growth, yield of carcass, intramuscular fat, marbling and yenderness.