While recent studies have identified higher than anticipated heterogeneity of mutation rate across genomic regions, mutations in exons and introns are assumed to be generated at the same rate. Here we find fewer somatic mutations in exons than expected from their sequence content and demonstrate that this is not due to purifying selection. Instead, we show that it is caused by higher mismatch-repair activity in exonic than in intronic regions. Our findings have important implications for understanding of mutational and DNA repair processes and knowledge of the evolution of eukaryotic genes, and they have practical ramifications for the study of evolution of both tumors and species.

中文翻译：

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由于差异错配修复，外显子突变率降低。

虽然最近的研究发现基因组区域的突变率异质性高于预期，但假设外显子和内含子的突变以相同的速率产生。在这里，我们发现外显子中的体细胞突变比从其序列内容中预期的要少，并证明这不是由于纯化选择。相反，我们表明它是由外显子中比内含子区域更高的错配修复活动引起的。我们的研究结果对于理解突变和 DNA 修复过程以及真核基因进化的知识具有重要意义，并且它们对研究肿瘤和物种的进化具有实际意义。