Gene survival in isolated populations: the number of distinct genes on Tristan da Cunha.

Gene extinction probabilities over the ancestral genealogy of Tristan da Cunha are analysed, to determine the probability distributions of numbers of surviving distinct founder genes. Autosomal, X-linked and Y-linked genes are considered, and also the bivariate distributions of genes originating in males and in females. One founder group shows a greater variety of surviving genes than another, although there is little difference in their total genetic contributions. This excess variety is concentrated in male lines of descent. The paper demonstrates the types of analysis that can be used to illuminate and summarize lists of gene extinction probabilities.