If Jane and John want to have another child, they plan to see a genetic counselor to find out when it would be best to test for galactosemia. A newborn with galactosemia must be put on a lactose- and galactose-free diet as soon as possible after birth. Even on this diet, affected individuals may still suffer from learning disabilities, ovarian failure (in young women), late-onset cataracts, and early death.
Which of the following tests would be most useful for Jane and John to have?
a. no testing
b. newborn screening (either assaying for the GALT enzyme or measuring excess galactose in the newborn’s blood)
c. carrier screening of Jane and John (to identify whether either or both of them carry the allele for galactosemia)
d. fetal chromosome analysis (examining fetal chromosomes for abnormalities as early as 11 weeks into the pregnancy