by one ethnic group or the other. Under ordinary circumstances when using genetic markers for a linkage analysis, it is more cumbersome to analyze families composed of individuals drawn from various ethnic groups because differences in allele frequencies need to be taken into account (see Suarez et al. [1] for an example of combining families of different ancestries in a linkage analysis). Using IBD matrices somewhat obviates this problem, although the possibility looms large that different ancestral populations may be segregating different causative genes.
