Trisomy 21 in man due to maternal non-disjunction during the first meiotic division.
D000328:Adult; D002648:Child; D002904:Chromosomes, Human, 21-22 and Y; D004314:Down Syndrome / Q000235:genetics*; D005111:Extrachromosomal Inheritance; D005260:Female; D006801:Humans; D007621:Karyotyping; D008297:Male; D008540:Meiosis