GENETIC IDENTITY COMBINING MUTATION AND DRIFT

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 estimate d directly from a data set. The new model is integrated into the exist ing body of population genetics theory. For an infinite population siz e the model becomes identical to the pure mutation model and if mutati on is neglected, it becomes equal to the well-known drift model. The p roposed measure of genetic identity between a population and its ances tral population is independent of the population size and equal to the number of ancestral alleles found in the present population. Using da ta on protein variability from ten primate species, it is shown that t he estimate of genetic identity proposed here correlates closely with other identity measures that do not consider genetic drift. The conclu sions from hitherto existing studies on the genetic similarity of spec ies, therefore, seem to be reliable. Finally, implications for estimat es of the ancestral degree of homozygosity are discussed.