Cytogenetic studies in families with two 47, +21-siblings.
D000293:Adolescent; D000328:Adult; D002648:Child; D002675:Child, Preschool; D002869:Chromosome Aberrations; D002904:Chromosomes, Human, 21-22 and Y; D004314:Down Syndrome / Q000235:genetics*; D005260:Female; D006801:Humans; D007223:Infant; D008297:Male; D008875:Middle Aged; D009030:Mosaicism; D010375:Pedigree; D014314:Trisomy