Gerber A S, Loggins R, Kumar S, Dowling T E
Department of Biology, University of North Dakota, Grand Forks, North Dakota 58202-9019, USA.
Annu Rev Genet. 2001;35:539-66. doi: 10.1146/annurev.genet.35.102401.091106.
Early studies of animal mitochondrial DNA (mtDNA) assumed that nucleotide sequence variation was neutral. Recent analyses of sequences from a variety of taxa have brought the validity of this assumption into question. Here we review analytical methods used to test for neutrality and evidence for nonneutral evolution of animal mtDNA. Evaluations of mitochondrial haplotypes in different nuclear backgrounds identified differences in performance, typically favoring coevolved mitochondrial and nuclear genomes. Experimental manipulations also indicated that certain haplotypes have an advantage over others; however, biotic and historical effects and cyto-nuclear interactions make it difficult to assess the relative importance of nonneutral factors. Statistical analyses of sequences have been used to argue for nonneutrality of mtDNA; however, rejection of neutral patterns in the published literature is common but not predominant. Patterns of replacement and synonymous substitutions within and between species identified a trend toward an excess of replacement mutations within species. This pattern has been viewed as support for the existence of mildly deleterious mutations within species; however, other alternative explanations that can produce similar patterns cannot be eliminated.
早期对动物线粒体DNA（mtDNA）的研究假定核苷酸序列变异是中性的。最近对来自各种分类群的序列分析对这一假设的有效性提出了质疑。在这里，我们回顾了用于测试中性的分析方法以及动物mtDNA非中性进化的证据。对不同核背景下线粒体单倍型的评估发现了性能上的差异，通常有利于共同进化的线粒体和核基因组。实验操作也表明某些单倍型比其他单倍型具有优势；然而，生物和历史效应以及细胞核相互作用使得难以评估非中性因素的相对重要性。对序列的统计分析已被用于论证mtDNA的非中性；然而，在已发表的文献中，拒绝中性模式很常见，但并非占主导地位。物种内部和物种之间的替换和同义替换模式表明，物种内部存在替换突变过多的趋势。这种模式被视为支持物种内部存在轻度有害突变；然而，不能排除其他能产生类似模式的替代解释。
