The contribution of slippage-like processes to genome evolution
The contribution of slippage-like processes to genome evolution
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DOI：
10.1007/bf00173185
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发表时间：
1995-12
影响因子：
3.9
通讯作者：
John M. Hancock
中科院分区：
文献类型：
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作者：
John M. Hancock
简单的序列存在于长（>30 kb）序列中，代表五个物种（智人、秀丽隐杆线虫、酿酒酵母、大肠杆菌）的单拷贝基因组。大肠杆菌和麻风分枝杆菌）进行了分析。观察到基因组大小和序列重复的总体水平之间存在密切关系。这表明简单序列的整合伴随着进化过程中基因组大小的增加。在真核生物中，非编码区的简单序列基序密度高于编码区，但在真细菌中则不然。所有五个基因组显示出非常偏见的频率分布的简单序列基序在所有物种中，特别是在真核生物中，AAA和TTT占主导地位。种间比较表明，非编码序列在真核生物中表现出高度显着相似的频率分布的简单序列基序，但这是不正确的编码序列。简单序列基序的频率分布的方差分析表明基序碱基组成和重复单元长度的贡献很大，但这些参数的变化仍然无法解释。因此，简单序列的序列组成似乎反映了滑动样过程中潜在的序列偏差和选择作用。编码序列中简单序列基序的频率分布与非编码序列中的频率分布相关性很弱或根本不相关。因此，对编码序列进行选择以消除不需要的序列可能是强有力的，特别是在人类谱系中。
Simple sequences present in long (>30 kb) sequences representative of the single-copy genome of five species (Homo sapiens, Caenorhabditis elegans Saccharomyces cerevisiae, E. coli, andMycobacterium leprae) have been analyzed. A close relationship was observed between genome size and the overall level of sequence repetition. This suggested that the incorporation of simple sequences had accompanied increases of genome size during evolution. Densities of simple sequence motifs were higher in noncoding regions than in coding regions in eukaryotes but not in eubacteria. All five genomes showed very biased frequency distributions of simple sequence motifs in all species, particularly in eukaryotes where AAA and TTT predominated. Interspecific comparisons showed that noncoding sequences in eukaryotes showed highly significantly similar frequency distributions of simple sequence motifs but this was not true of coding sequences. ANOVA of the frequency distributions of simple sequence motifs indicated strong contributions from motif base composition and repeat unit length, but much of the variation remained unexplained by these parameters. The sequence composition of simple sequences therefore appears to reflect both underlying sequence biases in slippage-like processes and the action of selection. Frequency distributions of simple sequence motifs in coding sequences correlated weakly or not at all with those in noncoding sequences. Selection on coding sequences to eliminate undesirable sequences may therefore have been strong, particularly in the human lineage.