Down syndrome is the most common genetic cause of intellectual disability. The complete phenotype is both complex, affecting multiple organs and organ systems, and highly variable in severity among individuals. Down syndrome is due to an extra copy of all or part of a normal chromosome 21 and the increased expression, due to gene dosage, of the normal genes encoded by it.

The large number of genes involved (>450), their functions and interactions, and the perturbations of cellular pathways and processes their increased expression causes, are challenges in determining gene-phenotype correlations.

This database and associated knowledge discovery tools are designed for researchers interested in individual chromosome 21 genes, groups of genes, their orthologues in models organisms, as well as Down syndrome and mouse models of Down syndrome.

The goal of the database is to facilitate research on human chromosome 21 and Down syndrome, and in this way, facilitate the development of therapeutics for the prevention or amelioration of phenotypic features. The approach is to:

• provide curated, annotated comprehensive information on chromosome 21 genes
• reduce redundant efforts in database and literature searches
• provide links to primary data sources for user evaluation
• provide new tools for data mining
• develop pathway annotation for chr21 proteins