The utility of simplex sibships in the characterization of HLA-linked disease susceptibility genes.

We demonstrate, by plotting the deviations from expected ratios of identity by descent (IBD) scores of sibling pairs having only one affected individual, that simplex pairs can, under certain constraints, provide a rich source of information concerning linkage relationships of a disease susceptibility gene. In addition, two statistical tests of significance are presented, one for a fixed sample size and a second for a sequential sampling approach.