Some caveats in the interpretation of   these results are in order. First, the nucleotide divergence statistics   describe the average pattern of molecular evolution. Individual codons may,   in many cases, deviate substantially from the norm. Second, for gene pairs   with S > 1, potentially large inaccuracies in the estimates of nucleotide   divergence are expected to result from multiple substitutions per site.   Nevertheless, as can be seen in Fig. 1, the patterns that we describe are   fully apparent within the subset of gene duplicates with S < 1. Third,   although we have taken special precautions to avoid the inclusion of   nonfunctional gene duplicates in our analyses (21), in the absence of actual   expression pattern data, we cannot be certain that all of the genes we have   included are functional. However, the fact that most of the pairs that we   have identified have R/S < 1 and that many pairs with small S have R/S >>   1.0 suggests that we have not inadvertently included many pseudogenes in our   analyses.

对这些结果的解释有些警惕是合理的。首先，核苷酸分异统计描述了分子进化的一般模式。在许多情况下，个别密码子可能实质上会偏离正常。第二，对于S>1的基因对，估计核苷酸差异的潜在大误差预计是由每个位点的多次替换引起的。然而，如图1所示，我们所描述的模式在S<1的基因重复子集中是很明显的。第三，尽管我们已经采取了特别的预防措施，以避免在我们的分析（21）中包含非功能基因重复，但在缺乏实际表达模式数据的情况下，我们不能确定我们所包含的所有基因都是功能性的。然而，我们发现的大多数重复基因的R/S <1，极小重复基因的R/S >>1.0表明我们在我们的分析并没有在无意中包含许多假基因。