COMPARING THE POWER OF LINKAGE DETECTION BY THE TRANSMISSION DISEQUILIBRIUM TEST AND THE IDENTITY-BY-DESCENT TEST

The aim of this study is to compare the power of the transmission dise quilibrium test (TDT) to that of the identity-by-descent (IBD) distrib ution test. The relative powers of these tests depend both on the unde rlying genetic model and on the available family data. Families with t wo affected sibs are always more informative than those with one affec ted child and one unaffected child. The IBD test is always more powerf ul in the first situation and, contrary to the TDT, is independent of the presence of gametic disequilibrium. When there is strong linkage d isequilibrium, the TDT can be more powerful than the IBD test. In that case, linkage can be detected by the TDT even in families with only o ne affected child. (C) 1995 Wiley-Liss, Inc.