中文摘要：

黄牛和牦牛远缘杂交后代犏牛雄性不育是牦牛杂交改良中的一大难题。Cdc2和Cdc25A是减数分裂的两个关键基因，其表达水平的下降将使精子发生不能正常进行，导致雄性不育。为了探讨Cdc2、Cdc25A基因mRNA表达水平与犏牛雄性不育的关系，文章采用荧光定量PCR技术对Cdc2和Cdc25A基因的组织表达特征以及在黄牛、牦牛和犏牛睾丸组织中的表达水平进行了分析。结果表明：Cdc2和Cdc25A基因在牦牛各种组织中广泛表达，说明Cdc2和Cdc25A基因在各种组织细胞分裂和细胞周期运行中均发挥作用；黄牛和牦牛睾丸组织中Cdc2、Cdc25A基因表达水平均显著高于犏牛（P〈0．05），说明睾丸组织中Cdc2和Cdc25A基因的低表达可能与犏牛雄性不育相关。

英文摘要：

The infertility of cattle-yak, which is the hybrid offspring of cattle and yak, is a difficult problem in crossbreeding and improvement of yak. Cdc2 and Cdc25A are the key genes of meiosis. The decline of their expression levels will cause the spermatogenesis failure and lead to infertility. Therefore, this study was conducted to study the relationship between the infertility of cattle-yak and the expression levels of Cdc2/Cdc25A genes. The expression profiles were obtained by RT-PCR. Cdc2 and Cdc25A genes were widely expressed in many tissues, which confirmed their important role in cell division and the progression of cell cycle. Real-time quantitative PCR analysis indicated that the expression levels of Cdc2 and Cdc25A in cattle and yak testis were higher than those in cattle-yak （P〈0.05）. Therefore, low expression levels of Cdc2 and Cdc25A genes may have a relationship with the infertility of cattle-yak.