Meiosis I non-disjunction as the main cause of trisomy 21.
The relative roles of Meiosis I and Meiosis II non-disjunctions in the causation of trisomy 21 have been assessed by analysing the distribution of polymorphic phenotypes of the chromosomes 21 in a group of individuals with Down's syndrome. The data suggest that the majority of cases of trisomy 21 are due to meiosis I non-disjunctions.
D002904:Chromosomes, Human, 21-22 and Y; D004314:Down Syndrome / Q000235:genetics*; D005453:Fluorescence; D006801:Humans; D008540:Meiosis; D011110:Polymorphism, Genetic