中文摘要：

研究了大肠杆菌和酿酒酵母两类生物全基因组的密码对，通过密码对的观察值与期望值的比较，发现密码对的使用有很强的偏好性；此外，按照Boycheva定义的标准（△REG）研究了密码对的使用与基因表达水平的关系，发现酵母与大肠杆菌两类生物的密码对使用与基因表达水平的关系是相似的；高表达基因偏好△REG为正值的密码对，而低表达基因偏好△REG为负值的密码对．通过曲线的相似性分析，可以推测，真核生物（Saccharomyces cerevisiae）与原核生物（Escherichia coli）在密码对的使用上，其机理是相似的．

英文摘要：

Codon pair usage in Escherichia coli and Saccharomyces cerevisiae genomes are studied. According to the comparison of codon pair usage frequencies between the real and statistically predicted frequencies of occurrence,a significant difference between them is observed; besides, according to an especially defined criterion （△REG） by Boycheva,the relations between codon pair usage and gene expression level are studied. The results show that the relations are similar for two species,the highly expressed genes tend to favor codon pairs with positive △REG values,whereas the codon pairs with negative △REG values are typical for the poorly expressed genes. From the similarity of the curves,it can be inferred that the mechanisms with respect to the codon pair usage are similar to E. coli （prokayote） and S. cerevisiae （eukaryote）.