Genetic identity combining mutation and drift

Abstract

A model for the genetic identity between diploid sexual populations is presented that considers simultaneously mutation and genetic drift as affecting gene frequencies. In contrast to other measures of genetic identity the proposed model allows the genetic identity to be estimated directly from a data set. The new model is integrated into the existing body of population genetics theory. For an infinite population size the model becomes identical to the pure mutation model and if mutation is neglected, it becomes equal to the well-known drift model. The proposed measure of genetic identity between a population and its ancestral population is independent of the population size and equal to the number of ancestral alleles found in the present population. Using data on protein variability from ten primate species, it is shown that the estimate of genetic identity proposed here correlates closely with other identity measures that do not consider genetic drift. The conclusions from hitherto existing studies on the genetic similarity of species, therefore, seem to be reliable. Finally, implications for estimates of the ancestral degree of homozygosity are discussed.