The chromosomal location of human DYRK1A, along with the phenotypic defects observed in the Dyrk1A+/− mutant mice that carry one copy of the murine homologue, suggest that DYRK1A might be a good candidate gene for some of the cases of partial monosomy 21 linked to mental retardation. The gene discussed is DYRK1A; the disease is Intellectual disability.