A team of researchers led by Gerard Schellenberg of theUniversity of Washington School of Medicine reported inFriday's issue of Science that they have mapped the genomiclocation of early-onset, familial Alzheimer's disease tochromosome 14.
The scientist haven't zeroed in on the genetic defect's preciselocation yet, but they have narrowed it down to thechromosomal marker D14S43, which is on the long arm ofchromosome 14.
Schellenberg and his associates assessed the inheritancepatterns of 64 different chromosomal markers by nine familieswith early-onset Alzheimer's. One of these markers inparticular -- D14S43 -- was clearly linked to the disease inseven of the nine families.
Scientists have recognized for at least five years thatAlzheimer's disease is not caused by a single genetic defect, butby two or more genes residing on different chromosomes."Additional familial Alzheimer's loci may exist on chromosome21 and chromosome 19, although these sites do not account forall familial Alzheimer's," according to the report. "FamilialAlzheimer's is indeed genetically heterogeneous."
The researchers still must wade through 10 million or so DNAbase pairs to "get the gene," but once they do, it may clear upsome of the questions that plague researchers regarding theetiology of this disease.
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