猪CAST基因的遗传多态性及遗传效应分析

采用PCR—SSCP方法对猪cAST基因遗传多态性进行分析。并研究基因型与肉质性状和背膘厚的相关性。根据猪CAST基因的cDNA序列（M20160）设计7对引物。结果在F1／R1。F6／R6引物对扩增的片段上发现了多态性。并对纯合子进行测序。发现317位A—G突变。2042位G—C突变。基因型在不同猪种分布的多重比较结果表明。长白猪、大白猪和杜洛克猪与沂蒙黑猪和莱芜猪比较差异极显著（P〈0．01）。固定效应模型分析结果表明，嫩度及背膘厚基因型间差异显著（P〈0．05），而pH值、温度及滴水损失基因型间差异不显著（P〉0．05）。最小二乘分析结果表明，不同猪种比较，屠宰12h和24h后肌肉温度、30min和1h后pH值及滴水损失差异显著（P〈0．05）；BBCC和BBDD单元型个体与其他单元型个体比较肌肉嫩度的差异显著（P〈0．01）。AACC和AADD单元型个体与其他单元型个体比较背膘厚的差异显著（P〈0．01）。因此，推测CAST基因对猪肉品质及背膘厚存在一定的影响。将CAST基因应用于猪育种过程中的标记辅助选择将可以改善猪肉品质。加快猪的育种进程。

GENETIC POLYMORPHISMS AND GENETIC EFFECTS OF CAST GENE IN PIGS

Single-nucleotide polymorphisms of the porcine CAST gene were tested using PCR-SSCP. Genetic effects of the CAST gene on the meat quality and the backfat thickness were analyzed. On the basis of the published cDNA sequence (M20 160) of the porcine CAST gene, seven pairs of primers were designed, and two polymorphisms were found in the PCR products amplified with F1/ R1, and F6/R6 primers. A --> G transition at 317 site, G --> C transition at 2042 site were detected by sequencing the homozygotes. The results show that: Firstly, the Landrace, the Large White, and the Duroc breeds differ significantly (P < 0.01) in haplotype distribution from the Laiwu and the Yimeng breeds. Secondly, on the basis of the fixed effect model, significant differences (P < 0.05) were found in the tenderness and the backfat thickness among the different CAST haplotypes, whereas no significant differences (P > 0.05) existed in the pH, the temperature and the drip loss. Thirdly, using least square analysis, it was seen that significant differences (P < 0.05) were found in the temperature at 12 h and 24 h postmortem, the pH at 30 min and 1 h postmortem and drip loss among different pig breeds. Individuals of the BBCC and BBDD haplotypes had significantly less (P < 0.01) tenderness than those of the other haplotypes, and the pigs of the AACC and AADD haplotypes had significantly higher (P < 0.01) backfat thickness than those of the other haplotypes. These results suggest that the genotype has significant effects on the meat quality and the backfat thickness. CAST can be used in marker-assisted selection to provide significant improvements for meat quality and to accelerate the breeding progress.