Why Is Trisomy 21 So Common?
Why Is Trisomy 21 So Common? Trisomy 21 (Down syndrome) is the most common autosomal trisomy in newborns, and is strongly associated with increasing maternal age. Trisomy 21 results most commonly from maternal meiotic nondisjunction. Unbalanced translocation accounts for up to 4% of cases. Why is Down syndrome the most common trisomy? Trisomy 21 –