title: Molecular structure of the number 21 chromosome and Down syndrome.
mesh_terms: D055598:Chemical Phenomena; D002621:Chemistry; D002869:Chromosome Aberrations / Q000235:genetics*; D025063:Chromosome Disorders; D002904:Chromosomes, Human, 21-22 and Y; D004314:Down Syndrome / Q000235:genetics*; D006801:Humans