Estimation of expected number of rare alleles of a locus and calculation of mutation rate.

An approach is described for the estimation of the number of rare variants in the population from the number in a sample drawn at random from the population. This quantity is used to derive an estimate of the mutation rate. The data required are the number of rare variants in the sample and the distribution of offspring within a population of well-defined size with little or no immigration. Application of this approach to data on 28 loci assayed in the Yanamamo, a tribe of South American Indians, yields an average mutation rate of 0.1 approximately 0.2 x 10(-5). Determination of this figure is subject to several assumptions concerning the nature of the rare variants and the structure of the population. Violation of these assumptions will generally result in the underestimate of the true mutation rate.