Fine mapping of an Alzheimer disease-associated gene encoding beta-amyloid protein.

We have sublocalized an Alzheimer Disease-associated gene, which encodes for cerebrovascular beta-amyloid protein, to the region from the centromere through the proximal half of band 21q21 using both somatic cell and in situ mapping techniques. In addition we found repeatedly significant but weaker hybridization of the beta-amyloid protein probe to the short arm of chromosome 20. 794 cells were analyzed from whole blood, lymphoblastoid and skin cultures. The latter two types of cultures had parts of the 21st chromosome translocated to other chromosomes facilitating sublocalization.