A couple has a child with Down syndrome.The mother is 39 years old at the time of delivery.Which of the following is the most probable cause of the child's condition?
A)The woman inherited this tendency from her parents.
B)One member of the couple carried a translocation.
C)Nondisjunction occurred in one member of the couple during somatic cell production.
D)Nondisjunction occurred in one member of the couple during gamete production.

Question

Quizplus · Accepted Answer

Down syndrome is most commonly caused by nondisjunction during gamete production, meaning that the individual has an extra copy of chromosome 21. Advanced maternal age is also a risk factor for having a child with Down syndrome, as the likelihood of nondisjunction increases with age. Inheriting the tendency from parents or a translocation in one member of the couple are less common causes of Down syndrome.

A Couple Has a Child with Down Syndrome