Chaturvedi Iti, Hlaing Mya Myintzu, Sing Lim Chu, Sakharkar Kishore R, Sakharkar Meena Kishore
Advanced design and modeling lab, Affiliated staff BioInformatics Research Centre, Nanyang Technological University, Singapore.
Front Biosci. 2007 May 1;12:3367-76. doi: 10.2741/2319.
Positive selection is usually considered in the context of a higher rate of substitutions in non-synonymous as compared to synonymous sites in complete coding sequences of genes or individual positions. We show that genes conserved in eukaryota, coelomata, and bilateria, that is, proteins that arose earlier in evolution as compared to mammalia specific genes evolve slowly and are subjected to negative selection. This finding supports the notion that evolutionary rates progressively diminish with the age of a gene. The data suggests that in both intron-containing and intronless genes synonymous sites may be subject to some degree of selection that is indicative of a relative acceleration of amino-acid substitution, which could be due to a relaxation of functional constraints and/or directional selection.
正向选择通常是在基因或单个位置的完整编码序列中，非同义位点的替换率高于同义位点的背景下进行考虑的。我们发现，在真核生物、体腔动物和两侧对称动物中保守的基因，即与哺乳动物特异性基因相比在进化中出现更早的蛋白质，进化缓慢且受到负向选择。这一发现支持了进化速率随着基因年龄的增长而逐渐降低的观点。数据表明，在含内含子和无内含子的基因中，同义位点可能都受到某种程度的选择，这表明氨基酸替换有相对加速的情况，这可能是由于功能限制的放松和/或定向选择所致。
