Foster P L, Eisenstadt E, Cairns J
Nature. 1982 Sep 23;299(5881):365-7. doi: 10.1038/299365a0.
The mutability of DNA varies enormously from one base pair to another. Part of this variation is due to the specificity of the reaction between mutagens and base, but much of the variation is due to unknown causes. A genetic system developed by Miller and colleagues allows the mutation frequencies of a large number of different base pairs in the lacI gene of Escherichia coli to be compared. For example, Coulondre and Miller found that the sites most readily mutated by UV light are almost 100 times more often mutated than the least susceptible sites. A recently completed study of mutagenesis with neocarzinostatin (NCS) in the lacI gene has prompted us to re-examine some previous studies, of mutagenesis in this gene. Our analysis, reported here, suggests that the mutations induced by certain mutagens fall into two classes: mutations in one class are clearly distributed non-randomly, that is, they are very common at some sites and significantly less common at others; mutations in the second class, however, occur at low frequency and appear to be randomly distributed. Both classes of mutations seem to occur only at damaged bases.
DNA的可突变性在不同碱基对之间差异极大。这种差异部分归因于诱变剂与碱基之间反应的特异性，但很大一部分差异是由未知原因造成的。米勒及其同事开发的一种遗传系统能够比较大肠杆菌lacI基因中大量不同碱基对的突变频率。例如，库隆德雷和米勒发现，紫外线最易诱变的位点发生突变的频率几乎是最不易受影响位点的100倍。最近一项关于新制癌菌素（NCS）对lacI基因诱变作用的研究促使我们重新审视该基因诱变作用的一些先前研究。我们在此报告的分析表明，某些诱变剂诱导的突变可分为两类：一类突变明显呈非随机分布，也就是说，它们在某些位点非常常见，而在其他位点则明显较少见；然而，第二类突变发生频率较低，似乎呈随机分布。这两类突变似乎都只发生在受损碱基处。
