Ju Zhi-Hua, Li Qiu-Ling, Wang Hong-Mei, Li Jian-Bin, An Li-Guo, Yang Gui-Wen, Zhong Ji-Feng, Wang Chang-Fa
1. Dairy Cattle Research Center, Shandong Academy of Agricultural Science, Jinan 250100, China; 2. Life Science College, Shandong Normal University, Jinan 250014, China E-mail:
Yi Chuan. 2008 Oct;30(10):1312-8. doi: 10.3724/sp.j.1005.2008.01312.
K-casein gene was regarded as a candidate gene for milk production traits of cows. In this study, a 779 bp fragment of k-casein gene of Chinese Holstein was amplified by polymerase chain reaction (PCR), the polymorphisms of three loci of k-casein gene were detected by PCR-RFLP with restriction endonuclease Taq, Hind, Pst. After sequencing, T/C single nucleotide polymorphism (SNP) was identified at nucleotide 10 891C/A SNP was identified at nucleotide 10 927 and G/A SNP was identified at nucleotide 10 988 in exon4 of k-casein gene. Both alleles (A and B) of three loci were found in the population that showed low polymorphism. The gene frequencies of A and B were 86.03% and 13.97%, respectively. The genotype frequencies of AA, AB, and BB were 73.71%, 24.63%, and 1.66%, respectively. Statistical results of c2 test indicated that three polymorphism sites in the population fitted with Hardy-Weinberg equilibrium (P > 0.05). Meanwhile, the effect of polymorphism of k-casein gene on milk production traits was analyzed. The results indicated that in the three loci, the different genotype of k-casein gene had no significant influence on milk yield and milk protein percent (P > 0.05). The cows with genotypes BB and AB showed higher milk fat percent than those with genotype AA ( P < 0.05 ) ; with genotype AB showed higher fat protein ratio than those with genotype AA ( P < 0.05 ). The polymorphism of the three loci in the experimental population is closely linked. The conclusion is that k-casein B allele can be used as the molecular genetic markers of modifying milk fat percent in Chinese Holstein cows.
κ-酪蛋白基因被视为奶牛产奶性状的候选基因。本研究采用聚合酶链反应（PCR）扩增中国荷斯坦牛κ-酪蛋白基因的一段779 bp片段，用限制性内切酶Taq、Hind、Pst通过PCR-RFLP检测κ-酪蛋白基因三个位点的多态性。测序后，在κ-酪蛋白基因外显子4的第10 891位核苷酸处鉴定出T/C单核苷酸多态性（SNP），在第10 927位核苷酸处鉴定出C/A SNP，在第10 988位核苷酸处鉴定出G/A SNP。在该群体中发现三个位点的两个等位基因（A和B），表现出低多态性。A和B的基因频率分别为86.03%和13.97%。AA、AB和BB的基因型频率分别为73.71%、24.63%和1.66%。χ²检验统计结果表明，群体中的三个多态性位点符合哈迪-温伯格平衡（P>0.05）。同时，分析了κ-酪蛋白基因多态性对产奶性状的影响。结果表明，在这三个位点中，κ-酪蛋白基因的不同基因型对产奶量和乳蛋白率没有显著影响（P>0.05）。基因型为BB和AB的奶牛乳脂率高于基因型为AA的奶牛（P<0.05）；基因型为AB的奶牛乳脂蛋白比高于基因型为AA的奶牛（P<0.05）。实验群体中三个位点的多态性紧密连锁。结论是，κ-酪蛋白B等位基因可作为改良中国荷斯坦奶牛乳脂率的分子遗传标记。
