中文摘要：

以生长分化因子9（Growth differentiation factor 9,GDF9）基因和骨形态发生蛋白15（Bone morphogenetic protein 15,BMP15）基因作为牛双胎性状的候选基因,研究了它们在鲁西牛、秦川牛、南阳牛和中国荷斯坦牛4个品种中的遗传变异,并在鲁西牛群体中研究了其多态位点与双胎性状的关系.结果表明：在鲁西牛中GDF9基因的3＇UTR发现缺失突变,而其它3个品种中没有发现该突变.对鲁西牛群体中该多态位点与单、双胎性状之间进行卡方显著性检验表明,单胎牛群体与双胎牛群体基因型分布有极显著的差异（P=0.006）,双胎牛群体的B等位基因频率明显大于单胎牛群体.通过生物信息学分析表明,突变体mRNA的二级结构与野生型相比总自由能值差异不大,但突变体mRNA翻译起始位点的二级结构稳定性明显大于野生型.在鲁西牛、南阳牛和秦川牛的BMP15基因中发现编码区第759～762 位有GAAA 4个碱基存在缺失突变,但没有检测到突变纯合个体,中国荷斯坦牛中没有检测到该突变.卡方显著性检验表明单胎牛群体和双胎牛群体在该位点基因型组成差异不显著（P=0.947）.

英文摘要：

Growth differentiation factor 9 （GDF9） gene and bone morphogenetic protein 15 （BMP15） gene were studied as candidate genes on the twinning trait in cattle. Genetic variation of GDF9 and BMP15 genes in Luxi cattle, Qinchuan cattle, Nanyang cattle and Chinese Holstein cattle was analyzed. The relationship between genetic polymorphisms and twinning trait was studied in Luxi cattle. The results showed that the 2-base deletion at 3＇UTR of GDF9 gene was only detected in Luxi cattle. The Х^2 test of association between genotypic distribution and twinning or monotocous trait in Luxi cattle showed significant difference （P=0. 006）. Frequency of B allele in Luxi twinning cows was higher than that in Luxi monotocous cows. According to bioinformatics analysis, the total free energy of the secondary structure of the mutation type mRNA was almost the same as the wild type mRNA. But the stability of the secondary structure in translation initiation region （TIR） of mutation type mRNA was significantly higher than that of wild type mRNA. 4-base deletion in coding sequence of BMP15 gene was detected in Luxi, Nan- yang and Qinchuan cattle. Homozygous mutation was not detected in these groups. The Х^2 test of association between genotypic distribution and twinning or monotocous trait in Luxi cattle showed no significant difference （P=0. 947）.