Slipped-strand mispairing: a major mechanism for DNA sequence evolution.
Slipped-strand mispairing: a major mechanism for DNA sequence evolution.
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DOI：
10.1093/oxfordjournals.molbev.a040442
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发表时间：
1987-05
影响因子：
10.7
通讯作者：
G. Gutman
中科院分区：
文献类型：
--
作者：
G. Gutman
简单重复DNA序列是基因组DNA的广泛和丰富的特征。这些序列具有以下几个特征：（1）它们通常由1-10个碱基的各种重复基序组成--但也可包括大得多的重复;（2）较大的重复单元内通常包括较短的重复单元;（3）通常发现长的多嘧啶和多CA束;（4）紧密相关基序的串联排列经常被发现。我们认为，滑动链错配事件，与不平等的交换相一致，可以很容易地解释所有这些特征。频繁发生的长串联重复的特定图案（聚嘧啶和聚CA道）似乎是由于非随机模式的核苷酸取代。我们认为，滑动链错配的螺旋内过程更有可能是短重复基序的初始扩展的主要因素，并且在初始扩展后，简单串联重复序列可能倾向于通过不平等的交叉或其他螺旋间事件进一步扩展，因为它们倾向于错配。有证据表明，单碱基重复序列（最短的可能的图案）是由哺乳动物内含子中的运行时间比预期的随机基础上，支持的想法，SSM可能是一个无处不在的力量在真核生物基因组的进化。因此，简单的重复序列可能代表未被选择用于编码功能的DNA的自然基态。
Simple repetitive DNA sequences are a widespread and abundant feature of genomic DNA. The following several features characterize such sequences: (1) they typically consist of a variety of repeated motifs of 1-10 bases--but may include much larger repeats as well; (2) larger repeat units often include shorter ones within them; (3) long polypyrimidine and poly-CA tracts are often found; and (4) tandem arrangements of closely related motifs are often found. We propose that slipped-strand mispairing events, in concert with unequal crossing-over, can readily account for all of these features. The frequent occurrence of long tandem repeats of particular motifs (polypyrimidine and poly-CA tracts) appears to result from nonrandom patterns of nucleotide substitution. We argue that the intrahelical process of slipped-strand mispairing is much more likely to be the major factor in the initial expansion of short repeated motifs and that, after initial expansion, simple tandem repeats may be predisposed to further expansion by unequal crossing-over or other interhelical events because of their propensity to mispair. Evidence is presented that single-base repeats (the shortest possible motifs) are represented by longer runs in mammalian introns than would be expected on a random basis, supporting the idea that SSM may be a ubiquitous force in the evolution of the eukaryotic genome. Simple repetitive sequences may therefore represent a natural ground state of DNA unselected for coding functions.