| With the release of the bovine genomic sequence and the development of molecular biology and techniques, it becomes more and more possible to breed animal at molecular level; the selection method tends to marker assisted selection, genomic selection which combine the markers'information with phenotypic information, from the traditional selection: Best Linear Unbiased Prediction (BLUP) which uses only phenotypic information; the markers become single nucleotide polymorphism (SNP) from early biochemical markers; and the genetic effects of candidate genes become more and more interested. The growth and meat quality are associated significantly with accumulation of fatty acids, in this study, five bovine genes were isolated and cloned using the approach of molecular biology combined with bioinformatics, the related information were obtained and the results were as the following:1. Using human cDNA sequences as query sequences, the homologous Expressed Sequence Tags (EST) were searched out from GenBank and assembled into contigs; the primers were designed according to the contigs or human cDNA sequences, the part of or full-length fragments of five bovine genes were isolated, these five genes are: acyl-malonyl condensing enzyme 1 (AMAC1), Acetyl-CoA carboxylases 1 (ACAA1), Acetyl-CoA carboxylases 2 (ACAA2), acyl-CoA dehydrogenase, member 8 (ACAD8) and acyl-Coenzyme A dehydrogenase, C-4 to C-12 straight chain (ACADM).2. The full-length cDNA sequences of AMAC1, ACAA1, ACAA2, ACAD8 and ACADM genes were obtained using Reverse Transcription Polymerase Chain Reaction (RT-PCR) and Allele-Specific PCR (AS-PCR), and the corresponding protein sequences were deduced and compared with some of other species close genetically. These five cDNA sequences have been submitted to GenBank, the accession numbers are: EU025856, EF576938, EF583004, DQ435444 and EU009460.3. Altogether seven SNPs of five genes: AMAC1, ACAA1, ACAA2, ACAD8 and ACADM were detected using PCR-RFLP and AS-PCR, and the allele frequencies and variation within and across different breeds were analysed.4. The association between production traits and the SNPs was analyzed with general linear model, the results show that: locus C201T and C291T of AMAC1 gene and locus A2009G of ACADM gene were not significantly associated with production traits (P>0.05); locus A1066G of ACAA1 gene was associated significantly with loin muscle area (P<0.05), the mean of genotype AA was the highest, genotype AG, second highest and genotype GG, the lowest, the mean of genotype AA was significantly different from that of genotype GG; locus A1452G was associated with loin muscle area, the mean of genotype GG was the highest, genotype AG, second highest and genotype AA, the lowest, the mean of genotype GG and AG were significantly different from that of genotype AA (P<0.05); locus A33119G of ACAA2 was associated with daily gain and loin muscle area (P<0.05), the mean of daily gain of genotype AG was higher significantly than genotype AA (P<0.05), the means of daily gain of genotype AA and AG were higher significantly than genotype GG (P<0.01), the means of loin muscle area of genotype AG and AA were not significantly different (P>0.05), both of them were lower than genotype GG (P<0.05); locus A13408G of ACAD8 gene was associated with daily gain and meat tenderness (P<0.05), the means of daily gain and tenderness of these three genotypes were significantly different from each other (P<0.05), the means of daily gain of genotype GG was the highest, genotype AG, second highest, genotype AA, the lowest; the relationship between these three genotype are contrary to tenderness, the means of genotype AA was the highest, genotype AG, second highest, genotype GG, the lowest.Part IIMeat quality traits, especially social traits, haven't clear economic values, but they are related closely to the flavor and consumption, and become an important part of breeding goal. In this study, more than 5000 Duroc×(Yorksire×Landrace) commercial animals of 12 families were used and Quantitative Trait Loci (QTL) linkage analysis was conducted for 6 meat quality traits with variance component analysis. 497 Single Nucleotide Polymorphisms (SNP) were used to construct the linkage map, spacing 5.48 cM averagely. The results of linkage analysis showed: altogether 37 QTLs were detected at 5% chrosome-wise significance level, among which 5 QTLs were associated with DRIP, 9QTLs associated with L*, 5 QTLs associated with PHI, 6 QTLs associated with PHK, 8 QTLs associated with a* and 4 QTLs associated with b*; 12 of 37 QTLs were significant at 5% genome-wise level. Most QTLs can account for 1-2% of total phenotypic variance. There are 4 QTLs which can account for more than 4% of total phenotypic variance, they are QTL affecting DRIP on SSC2, QTL affecting PHI on SSC6, QTL affecting PHK on SSC6, and QTL affecting b* on SSC1. Some genetically correlated traits have quite similar likelihood profiles on some chromosomes, and QTL effects of these traits are highly correlated, indicating these traits are regulated by the same gene with a great possibility. Most QTLs were segregated in 3 or 4 families and their 95% confidential interval were wide (>30 cM). Some strategies for fine mapping were presented based on the genome scan results. |
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