Having trouble answering these questions.
John and Jane Jones’ newborn baby girl, Leah, has just been diagnosed with galactosemia. Prior to their genetic counseling appointment, they submitted this family history:
- John and Jane’s older child, a son named Lee, does not have galactosemia.
- John is the only child of Hanna and Harry.
- Harry was an only child. Hanna has two older sisters, Hope (the oldest) and Holly.
- Both Harry and Hanna’s parents lived in good health into their 80s.
- Jane’s brother, Joe, is married to Jen. They have a son, Les, who is a healthy nine-year-old with myopia (nearsightedness) but no sign of galactosemia.
- Jane’s mother, Hilda, is alive and healthy; Jane’s father, Henry, passed away last year of a sudden heart attack. Hilda and Henry have no family history of galactosemia.
Use the information in the family history to construct a pedigree for this family.
Based on the inheritance pattern, which mode of inheritance must be the cause of galactosemia?
sex-linked dominant
autosomal recessive
autosomal dominant
sex-linked recessive
Jane and John are considering having another child. Given the pedigree you constructed and the mode of inheritance for galactosemia, what is the risk that their next child will have the disorder?
1/4 (because they are both heterozygotes)
1/16 (because they each have 1/4 chance of passing on the allele)
0 (because they already have one child with the disorder)
3/4 (because they are both heterozygotes)
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?
fetal chromosome analysis (examining fetal chromosomes for abnormalities as early as 11 weeks into the pregnancy)
newborn screening (either assaying for the GALT enzyme or measuring excess galactose in the newborn’s blood)
no testing
carrier screening of Jane and John (to identify whether either or both of them carry the allele for galactosemia)
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