MyoD基因对肉牛胴体性状影响的分析

用PCR技术克隆到MyoD基因的第二内含子, 采用PCR-SSCP方法研究了3个黄牛品种(鲁西牛、晋喃牛、秦川牛)及4个杂交肉牛(夏洛莱×鲁西牛、安格斯×鲁西牛、利木赞×鲁西牛、西门塔尔×鲁西牛)群体MyoD基因的多态性, 并分析了基因位点多态性与肉牛肉质性状的相关性。实验结果,在国内首次扩增出肉牛MyoD基因的第二内含子的全部序列, 共261 bp。用SSCP方法检测到MyoD基因内含子2有A和B两个等位基因。测序结果表明该座位的多态性是由于内含子二39 bp处C-T的突变和112 bp处C→G的突变造成的。等位基因B在中国地方品种的分布频率高于引进品种的杂交牛群体。c2检验的结果表明, 在该位点的除夏洛莱和安格斯杂交牛外, 其余五个群体(晋南、鲁西、秦川、西门塔尔杂交牛和利木赞杂交牛)均处于Hardy-Weinberg不平衡状态(P>0.05)。实验群体不同基因型与肉牛的宰前活重、胴体重、净肉重、高档肉重、眼肌面积等性状的影响差异极显著或显著(P<0.01或P<0.05), 并且AA型个体均高于AB型个体。

Relationship between genotypes at MyoD locus and carcass traits in cattle

A 261 bp sequence of the bovine MyoD gene intron 2 was cloned and was found to bear no similarities to the human MyoD gene sequence. Polymorphisms of the Myod gene in cattle including three Chinese breeds (Luxi cattle, Jinnan cattle and Qinchuan cattle) and four cross-breeding populations (Limousin x Luxi cattle, Simmental x Luxi cattle, Charolais x Luxi cattle and Angus x Luxi cattle) were detected by PCR-SSCP. Two SSCP alleles (A and B) were detected, which caused by a C-->T at 39 bp and a C-->G transition at 112 bp. Only two genotypes AA and AB occurred in the population. In Chinese local cattle, B allele was dominant, and this locus was at Hardy-Weinberg equilibrium except for the Charolais x Luxi cattle and Angus x Luxi cattle. The association of these polymorphisms with cattle carcass traits was analyzed using the general linear model (GLM). Statistical analysis revealed a higher value of living weight, carcass weight and loin eye area for individuals with genotype AA than AB (P < 0.05). Further studies on a bigger population size are needed to confirm the observed effect of MyoD genotypes on carcass quality traits.