A conservative viewpoint on linkage in Alzheimer's disease.

Linkage data in Alzheimer's disease have not firmly established a genetic locus on chromosome 21 in early onset disease families. There is little or no support for a chromosome 21 locus in late onset families. Differences in the selection of families and the analysis of data accounts for the differences in interpretation. The actual location of a genetic locus (or loci) for Alzheimer's disease in the human genome will not be influenced by this controversy; more data from exclusion mapping and the use of several methods of linkage analysis will answer current questions.