Francino M P, Chao L, Riley M A, Ochman H
Department of Biology, University of Rochester, NY 14627, USA.
Science. 1996 Apr 5;272(5258):107-9. doi: 10.1126/science.272.5258.107.
Although certain replication errors occur at different frequencies on each of the complementary strands of DNA, it remains unclear whether this bias is prevalent enough during chromosome replication to affect sequence evolution. Here, nucleotide substitutions in enteric bacteria were examined, and no difference in mutation rates was detected between the leading and lagging strands, but in comparing the coding and noncoding strands, and excess of C-->T changes was observed on the coding strand. This asymmetry is best explained by transcription-coupled repair on the noncoding strand. Although the vast majority of mutations are thought to arise from spontaneous errors during replication, this result implicates DNA damage as a substantial source of mutations in the wild.
尽管某些复制错误在DNA的每条互补链上出现的频率不同，但目前尚不清楚这种偏差在染色体复制过程中是否普遍到足以影响序列进化。在这里，对肠道细菌中的核苷酸替换进行了研究，结果发现前导链和后随链之间的突变率没有差异，但在比较编码链和非编码链时，观察到编码链上存在过量的C→T变化。这种不对称性最好用非编码链上的转录偶联修复来解释。尽管绝大多数突变被认为是在复制过程中由自发错误产生的，但这一结果表明DNA损伤是野生环境中突变的一个重要来源。
