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依据基因表达水平的理论预测方法从１３７３个大肠杆菌基因中选出了７３个甚高表达基因和１００个甚低表达基因．研究了这两类基因编码区起始密码子ＡＴＧ前－１到－２１位点（包含ＳＤ序列）的碱基构成与基因表达水平的关系．结果表明，ＳＤ序列中的富嘌呤区（约在－７到－１２位点）Ｇ和Ｔ的概率分布曲线中心到ＡＴＧ的距离（记为ＬＨ）与基因表达水平有明显的关系．甚高表达基因ＬＨ约为１０，甚低表达基因的ＬＨ约为８；另外在－１位点处，高低表达基因的Ｔ或Ｃ出现的概率有明显的差异
Based on the theoretical prediction of gene expression, 73 highly expressed genes and 100 very low expressed genes were selected from 1373 E. coli genes. The relationship between the base composition and the gene expression level of ATG from -1 to -21 (including the SD sequence) of ATG in the coding region of these two genes was studied. The results show that there is a clear relationship between the distance from the center of ATG to the ATG (denoted LH) in the G-sequence of the purine (about -7 to -12 sites) in the SD sequence and the gene expression level. The highly expressed gene LH was about 10, and the very low expressed gene LH was about 8. In addition, there was a significant difference in the probability of occurrence of T or C at the -1 locus