TEMPO AND MODE OF SEQUENCE EVOLUTION IN MITOCHONDRIAL-DNA OF HAWAIIAN DROSOPHILA
TEMPO AND MODE OF SEQUENCE EVOLUTION IN MITOCHONDRIAL-DNA OF HAWAIIAN DROSOPHILA
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DOI：
10.1007/bf02111289
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发表时间：
1987-01-01
影响因子：
3.9
通讯作者：
WILSON, AC
中科院分区：
文献类型：
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作者：
DESALLE, R;FREEDMAN, T;WILSON, AC
对14种夏威夷果蝇和5种其它双翅目昆虫的667 bp的DNA进行了序列比较。这些序列包括NADH脱氢酶（亚基1、2和5）和rRNA（来自核糖体大亚基）的部分基因。由于这些物种之间的分歧时间是已知的近似，序列比较可以深入了解这种分子的进化动力学。转换解释了几乎所有的序列之间的差异，分歧小于2%，这些序列的平均分歧率似乎是约2%/百万年。在涉及更大的分歧时间和更大的序列分歧的比较中，相对更多的序列差异是由于颠换。具体来说，这些差异中被视为颠换的部分从小于0.1的初始值上升到接近0.6的平台值。达到一半的平台值所需的时间，约为10万年，与哺乳动物mtDNA相似。果蝇和哺乳动物的mtDNA在蛋白质编码区差异位置的百分比与分化时间的曲线形状上也是相似的。对于两组动物，曲线具有归因于同义置换的快速积累的陡峭的初始斜率和由引起氨基酸置换的置换的缓慢积累引起的浅的最终斜率。然而，在所有位点中，可以经历高替换率的位点的百分比似乎只有约8%，而哺乳动物mtDNA约为20%。高变位点的低百分比可能是与果蝇mtDNA中鸟嘌呤和胞嘧啶含量低相关的功能限制的结果。
Sequence comparisons were made for up to 667 bp of DNA cloned from 14 kinds of HawaiianDrosophilaand five other dipteran species. These sequences include parts of the genes for NADH dehydrogenase (subunits 1, 2, and 5) and rRNA (from the large ribosomal subunit). Because the times of divergence among these species are known approximately, the sequence comparisons give insight into the evolutionary dynamics of this molecule. Transitions account for nearly all of the differences between sequences that have diverged by less than 2%; for these sequences the mean rate of divergence appears to be about 2%/Myr. In comparisons involving greater divergence times and greater sequence divergence, relatively more of the sequence differences are due to transversions. Specifically, the fraction of these differences that are counted as transversions rises from an initial value of less than 0.1 to a plateau value of nearly 0.6. The time required to reach half of the plateau value, about 10 Myr, is similar to that for mammalian mtDNA. The mtDNAs of flies and mammals are also alike in the shape of the curve relating the percentage of positions at which there are differences in protein-coding regions to the time of divergence. For both groups of animals, the curve has a steep initial slope ascribable to fast accumulation of synonymous substitutions and a shallow final slope resulting from the slow accumulation of substitutions causing amino acid replacements. However, the percentage of all sites that can experience a high rate of substitution appears to be only about 8% for fly mtDNA compared to about 20% for mammalian mtDNA. The low percentage of hypervariable sites may be a consequence of a functional constraint associated with the low content of guanine and cytosine in fly mtDNA.