title: Maternal and paternal origin of extra chromosome in trisomy 21.
abstract: Fluorescence markers were studied in 40 patients with Down's syndrome and their parents. In 11 cases maternal and in 5 cases paternal non-disjunction could be shown. The disjunctional event occurred in the first meiotic division in 5 maternal and in 2 paternal cases. A second division failure was found in 4 maternal and 2 paternal cases. In 3 cases the failure could either be of first or second meiotic division origin.
mesh_terms: D000328:Adult; D000367:Age Factors; D002904:Chromosomes, Human, 21-22 and Y; D004314:Down Syndrome / Q000235:genetics*; D005260:Female; D006801:Humans; D008297:Male; D008540:Meiosis; D010290:Parents; D010375:Pedigree; D012737:Sex Factors