Sharp P M, Shields D C, Wolfe K H, Li W H
Department of Genetics, Trinity College, Dublin, Ireland.
Science. 1989 Nov 10;246(4931):808-10. doi: 10.1126/science.2683084.
The basal rate of DNA sequence evolution in enterobacteria, as seen in the extent of divergence between Escherichia coli and Salmonella typhimurium, varies greatly among genes, even when only "silent" sites are considered. The degree of divergence is clearly related to the level of gene expression, reflecting constraints on synonymous codon choice. However, where this constraint is weak, among genes not expressed at high levels, divergence is also related to the chromosomal location of the gene; it appears that genes furthest away from oriC, the origin of replication, have a mutation rate approximately two times that of genes near oriC.
从大肠杆菌和鼠伤寒沙门氏菌之间的差异程度可以看出，肠道细菌中DNA序列进化的基础速率在不同基因间差异很大，即便只考虑“沉默”位点也是如此。差异程度明显与基因表达水平相关，这反映了对同义密码子选择的限制。然而，在这种限制较弱的情况下，即在那些不高水平表达的基因中，差异也与基因的染色体位置有关；似乎距离复制起点oriC最远的基因，其突变率大约是靠近oriC的基因的两倍。
