Estimating ancestral population parameters.
Estimating ancestral population parameters.
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作者：
J. Wakeley;Jody Hey
不同类别的多态性位点的预期数量来自两个相关的模型的人口历史的隔离模型，其中一个祖先的人口分裂成两个后代，和大小变化模型，其中一个单一的人口经历了瞬间的大小变化。对于隔离模型，所观察到的共享，固定和排他性多态位点的数量被用来估计三个种群的相对大小，祖先加两个后代，以及分裂的时间。对于大小变化模型，样本中以特定频率分离的位点的数量被用来估计祖先和后代种群的相对大小加上变化发生的时间。通过选择最接近地将期望与观测等同的值来估计参数。计算机模拟表明，当前和历史的人口参数可以准确地估计。该方法适用于从两个物种的果蝇和一些人的线粒体DNA序列的DNA数据。
The expected numbers of different categories of polymorphic sites are derived for two related models of population history the isolation model, in which an ancestral population splits into two descendents, and the size-change model, in which a single population undergoes an instantaneous change in size. For the isolation model, the observed numbers of shared, fixed, and exclusive polymorphic sites are used to estimate the relative sizes of the three populations, ancestral plus two descendent, as well as the time of the split. For the size change model, the numbers of sites segregating at particular frequencies in the sample are used to estimate the relative sizes of the ancestral and descendent populations plus the time the change took place. Parameters are estimated by choosing values that most closely equate expectations with observations. Computer simulations show that current and historical population parameters can be estimated accurately. The methods are applied to DNA data from two species of Drosophila and to some human mitochondrial DNA sequences.