Non-disjunction in trisomy 21: study of chromosomal heteromorphisms in 110 families.
QM variants on chromosome 21 and silver staining of NOR regions were applied in the study of non-disjunction in 110 families from different parts of Denmark. In 76% of the families the study was informative. Paternal failures were observed in 11% on Funen as compared 23.5% on Zealand. In one family, crossing-over on the short arms of chromosome 21 in the mother and mitotic non-disjunction of chromosome 21 was observed. Maternal first meiotic error predominates in both high maternal and low maternal age. Also in paternal non-disjunction failures of first meiotic division predominate. Two maternally and one paternally originated cases of de novo translocations were observed.
D000293:Adolescent; D000328:Adult; D002648:Child; D002675:Child, Preschool; D002904:Chromosomes, Human, 21-22 and Y / Q000648:ultrastructure; D004314:Down Syndrome / Q000235:genetics*; D005260:Female; D006801:Humans; D007621:Karyotyping; D008297:Male; D008423:Maternal Age; D009630:Nondisjunction, Genetic; D010331:Paternal Age