摘要：From two aspects the composition of nucleotides of codon - pairs and codon usage, thepreferential and rare codon - pairs usage was analyzed in 6 mode species genomes. The results indicated thatin regard to the preferential codon - pairs, the dinucleotide TA had the least occurrence frequenc, and that the dinucleotide whose occurrence frequency was the most highest was different from Archaea, Bacteriaand Eukaryota; In regard to the rare codon -pairs,however,the occurrence frequency of the dinucleotideTAwas the most highest,and that the dinucleotides whose occurrence fequency was the least were differentfrom Archaea, Bacteria and Eukaryota. The results showed that the dinucleotides distribution wassignificantly relative with the codon - pair bias. Besides, the correlation between theoccurrence frequenciesof the preferential and rare codon - pairs and the codon usage was analyzed, it was found that thecodon - pairs occurrence frequency wasassociated with the codon usage.%以6种模式生物基因组为样本,从密码对的碱基组成及密码子的使用两方面,分析了最适密码对与稀有密码对的使用.结果显示:6种生物的最适密码对rP双碱基TA出现的频数都是最低的,而出现频率最大的双碱墓对于古菌、细菌、真核是不同的；稀有密码对中双碱基TA出现的频数却是最高的,而出现频率最低的双碱基刘·于古菌、细菌、真核是不同的.这说明双碱基的分布与密码对的偏好性有很强的相关性,同时也与基因组进化存在关联.另外,我们也分析了本文的6种生物编码序列叶,最适密码对与稀有密码对的出现频数与密码了的相对使用频率的关系,发现密码对的出现频数与其密码子的使用存在相关性.
