Probability of founder effect in a tribal population.

Abstract

When an unusually high frequency of an allele is encountered in a population, founder effect is often invoked as an explanation. The term implies the disproportionate increase through chance (rather than selection) of an allele contributed to the population by a particular ancestor. While genetic theory leaves no doubt this is a possible explanation, problems arise when an attempt is made to determine how likely this explanation is for any specific finding in any specific, finite population, i.e., just how rare is this rare event? In this communication the question is considered in the context of Amerindian tribal populations, deriving specific probabilities under defined conditions. Interest in the question was whetted by the finding to date of some 8 possible examples of a founder effect in studies of 12 different tribes.