Early in Their Marriage, in Their Mid-20s, Charles and Leona

Essay

Early in their marriage, in their mid-20s, Charles and Leona had two normal children, a boy and girl. Later, when Charles and Leona were both 42 years old, Leona unexpectedly became pregnant again, despite the birth control methods the couple had practiced for many years. Both parents were in good physical health and there was no history of genetic disorders in either of their families. Still, they wondered about the risks of a genetic or chromosomal disorder in their child-to-be. (a) What might a genetic counselor tell the parents about their chances of having a child with Down syndrome? (b) What methods might be employed to determine if the fetus is normal prior to birth? (c) What other kinds of defects might these methods detect?