The traditional approach to inferring the   magnitude of selective constraint on protein evolution focuses on codons,   comparing the rates of nucleotide substitution at replacement and silent   sites (7, 15, 16). With this sort of analysis, only the cumulative pattern of   nucleotide substitution is identified, making it difficult to determine   whether duplicate genes typically undergo different phases of evolutionary   divergence, e.g., an early phase of near neutrality followed by a later phase   of selective constraint. Some clarification of this issue can be achieved by   considering the features of sets of gene duplicates separated by an array of   divergence times.

传统的推断蛋白质进化的选择性限制的方法集中在密码子上，比较功能变化位点和沉默位点的核苷酸替换比率（7，15，16）。通过这种分析，仅识别出核苷酸替换的累积模式，使得很难确定重复基因是否典型地经历不同的进化分化阶段，例如，接近中性的早期阶段，随后是选择性限制的后期阶段。通过考虑由一系列分化时间不同的重复基因（见编者注），可以对这个问题进行一些澄清。