Functional genomics of the Down syndrome

Down syndrome, as a phenotypic result of trisomy 21, is a complex condition with a set of over 30 phenotypic features, wh ich manifest themselves with varying frequencies among affected individuals. The importance for molecul ar medicine of understanding the molecular mechanisms underlying Down syndr ome becomes fully appreciated when a striking feature of Down syndrome is t aken into account: that the overdose of otherwise perfectly normal genes ca uses disorders of human health, indistinguishable from major public health problems of the general population, such as mandatory early onset Alzheimer 's degeneration, increased risk of leukemia, and protection from cancer of solid tissues. The DNA sequence of human chromosome 21 is, at the moment, t he most complete piece of DNA sequence known in the whole of human genome. The challenge for the future is an integrated, multidisciplinary approach t o the molecular biology of chromosome 21 genes, in conjunction with the res earch into the variation in their genotype, expression, and function in the normal population, in Down syndrome individuals with well-characterized ph enotypic traits, and in euploid patients suffering from diseases associated with phenotypic components of Down syndrome: mental retardation, developme ntal defects, hematological and solid tissue malignancies, and Alzheimer's disease.