Acouple 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 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? one of the gametes in the mother most likely underwent nondisjunction during meiosis. the mother had a chromosomal duplication. the woman inherited this tendency from her parents. one member of the couple underwent nondisjunction in somatic cell production.