Holmquist R, Goodman M, Conroy T, Czelusniak J
J Mol Evol. 1983;19(6):437-48. doi: 10.1007/BF02102319.
We have examined the extensive amino acid sequence data now available for five protein families - the alpha crystallin A chain, myoglobin, alpha and beta hemoglobin, and the cytochromes c - with the goal of estimating the true spatial distribution of base substitutions within genes that code for proteins. In every case the commonly used Poisson density failed to even approximate the experimental pattern of base substitution. For the 87 species of beta hemoglobin examined, for example, the probability that the observed results were from a Poisson process was the minuscule 10(-44). Analogous results were obtained for the other functional families. All the data were reasonably, but not perfectly, described by the negative binomial density. In particular, most of the data were described by one of the very simple limiting forms of this density, the geometric density. The implications of this for evolutionary inference are discussed. It is evident that most estimates of total base substitutions between genes are badly in need of revision.
我们已研究了目前可获得的五个蛋白质家族的大量氨基酸序列数据，这五个家族分别是α晶状体蛋白A链、肌红蛋白、α和β血红蛋白以及细胞色素c，目的是估计编码蛋白质的基因内碱基替换的真实空间分布。在每种情况下，常用的泊松密度甚至都无法近似碱基替换的实验模式。例如，对于所检测的87种β血红蛋白，观察结果来自泊松过程的概率极小，为10的负44次方。其他功能家族也得到了类似结果。所有数据都能被负二项分布密度合理但并非完美地描述。特别是，大多数数据可用这种密度的一种非常简单的极限形式，即几何分布密度来描述。文中讨论了这对进化推断的影响。显然，基因间总碱基替换的大多数估计都急需修正。
