PERSPECTIVES OF IDENTITY BY DESCENT (IBD) MAPPING IN FOUNDER POPULATIONS

In a founder population patients with a genetic disease are likely to share predisposing genes from a common ancestor. We show that, dependi ng on the distance of the relationship, patients are expected to share extended segments of DNA around the disease gene. Because of the size of the shared segment, a genomic search with DNA markers for such sha red segments, identity by descent (IBD) mapping, can efficiently find the map position of genes, particularly due to genetic drift leading t o reduction of heterogeneity and the large number of meioses that is i mplicitly observed. The statistical power of this method and the appro ximate cost are given as a function of the density of the map of teste d markers and the number of generations since a common ancestor. Initi al marker spacings between 5 and 15 centiMorgans are shown to be optim al. IBD mapping is applicable to many genetic diseases, because it doe s not presuppose a specific genetic model.