02-14-2007, 01:11 AM
The only way that the child could have three chromosomes 21s which are all distinguishable by C-banding is to have inherited two from the father, and one from the mother (remember, mother's chromosome 21s cannot be distinguished by this banding technique). Thus non-disjunction must have occured paternal line. Inorder for the father
to contain two different chromosomes 21s the non-disjunction event would have to occure meiosis I. If it had occured in meiosis II, then themost likelly the father would have donated two identical chromosomes 21s which would not distigushable by the C-banding.
to contain two different chromosomes 21s the non-disjunction event would have to occure meiosis I. If it had occured in meiosis II, then themost likelly the father would have donated two identical chromosomes 21s which would not distigushable by the C-banding.