[Absence of linkage between Alzheimer's disease and a polymorphic probe of the long arm of chromosome 21].

The hypothesis of an eventual linkage between Alzheimer's disease (AD), a presenile dementia, and the genomic probe GMG 21 S3, located on the long arm of chromosome 21, has been investigated in a large family originating from Calabria, in which AD is transmitted as an autosomal dominant mendelian trait. Analysis of the Bgl II restriction polymorphism, after molecular hybridization with the probe, of DNAs coming from 28 subjects of a pedigree, from which 10 individuals are affected, allowed to demonstrate that there wasn't any linkage between AD and the marker studied.