DNA进化马尔可夫过程模型的评价与推广  

Evaluation and Extension of Markov Process Models for the Evolution of DNA

作　　者：杨子恒[1] Goldm.,N 

机构地区：[1]北京农业大学畜牧系

出　　处：《Acta Genetica Sinica》1994年第1期17-23,共7页

摘　　要：本文对ＤＮＡ序列进化过程中核苷酸替代的随机模型进行了评价，对替代速率在时间和空间上不恒定的情形进行了考察与推广。Ｌａｎａｖｅ等（１９８４）曾提出一个模型，宣称对替代的模式未做任何假定，但事实上我们证明它假定替代过程是可逆的。运用２－ｐ、４－ｐ和６－ｐ模型进行的计算表明替代速度在位点间的差异会造成估计的替代数严重偏低，并且替代数越大，偏差也越大。替代模式在位点间的差异也会造成估计值偏低，但偏差不严重。运用非齐次马氏过程模型研究了替代速度在时间上的变异，结果表明估计的替代数反映了速率在时间上的平均值。文中还讨论了本文结果与进化树推断的关系。Markov process models of nucleotide substitution are evaluated.Amodel proposed by Lanave et al (1984), alleged to need no priori assumption about the substitution pattern,is found to have the assumption of reversibility. Calculations based on the 2-p,4-p, and 6-p substitution schemes show that site variation of substitution speed leads to serious under-estimation of sequence divergence by various methods. Spatial pattern variation also leads to under-estimation, but the discrepancy is slight.A nonhomogeneous Markov process model is used to study the temporal variations of rates and it is shown that the estimated number of substitutions reflects a rate averaged over time. The implications of those results to evolutionary phylogenetics are discussed.

关 键 词：随机过程模型 分子进化 DNA 

分 类 号：Q342[生物学—遗传学]