大肠杆菌编码区5′端碱基的统计分析

统计了大肠杆菌１２８８个编码序列开始的３３个碱基位点（１１个密码子）上各碱基出现的概率，发现第２、第３密码子各位点上的碱基概率分布与其它密码子上的碱基分布概率不一样；碱基Ｇ和Ｔ出现的概率从第４个密码子后呈现明显的３周期分布．我们还研究了这些位点上的碱基概率分布与基因表达水平的关系，发现高表达基因和低表达基因在第２、第３密码子各位点上，其各种碱基的概率分布是有区别的；高表达基因碱基Ｇ和Ｔ的概率分布３周期性更明显．

The Statistical Analysis on the Bases in Coding Start Region of E.coli Genes

The 1 288 beginning sequences in gene coding region of Escherichia coli are compiled and the probability of bases in site 1 to site 33 are calculated.We find that the probability distribution of bases in each base site of second and third condon are different from the others;At the beginning of the fourth codon,the probabilities of bases G and base T in each site of codons have distinctly 3 period distribution.The relation between the probability distribution of bases in these sites and gene expression level are studied.The results show that the probability distribution of bases in codon 2 and codon 3 have differences between high and low expressed genes;Its 3 period distribution of base G and T for high expressed genes are more distinct than low expressed genes.