Brown G G, Simpson M V
Proc Natl Acad Sci U S A. 1982 May;79(10):3246-50. doi: 10.1073/pnas.79.10.3246.
The sequence of the region of the mitochondrial genome that encodes cytochrome oxidase subunit II (COII) has been determined for each of two closely related rat species, Rattus norvegicus and R. rattus. Comparison of the two sequences shows that 94.4% of the nucleotide substitutions are silent. The occurrence of this high proportion of silent substitutions leads us to propose that the rapid evolution of mtDNA relative to nuclear DNA is due only to silent changes and that amino acid-altering substitutions accumulate in nuclear and mtDNA at comparable rates. Other novel features of the nucleotide substitution pattern in the rat COII gene are a high transition/transversion ratio (8.0:1) and a strong bias toward C in equilibrium T transitions in the light strand. Comparison of the R. norvegicus COII sequence with the bovine and human sequences show that there may be selective constraints on some silent positions within the gene and that its rate of evolution may be different in different mammalian lineages.
已确定了两种近缘大鼠物种(褐家鼠和黑家鼠)线粒体基因组中编码细胞色素氧化酶亚基II(COII)区域的序列。对这两个序列的比较表明,94.4%的核苷酸替换是沉默替换。这种高比例沉默替换的出现使我们提出,相对于核DNA而言,线粒体DNA的快速进化仅归因于沉默变化,并且氨基酸改变替换在核DNA和线粒体DNA中以相当的速率积累。大鼠COII基因核苷酸替换模式的其他新特征是高转换/颠换比(8.0:1)以及轻链中平衡T转换对C的强烈偏向。将褐家鼠的COII序列与牛和人的序列进行比较表明,该基因内的一些沉默位点可能存在选择限制,并且其进化速率在不同的哺乳动物谱系中可能不同。