Functional analysis of genes implicated in Down syndrome: 1. Cognitive abilities in mice transpolygenic for Down Syndrome Chromosomal Region-1 (DCR-1).

Down syndrome occurs every 1/1000 births and is the most frequent genetic cause of mental retardation. The genetic substrate of Down syndrome, an extra chromosome 21, was discovered by Lejeune, half-a-century ago, and the chromosome has been fully sequenced, although the gene(s) implicated in the mental retardation observed with the syndrome are still unknown. Observations of patients with partial trisomy of the 21q22.