KROK 1 Stomatology 2016 – Question 141 · KROK (Dentistry)
Phenylketonuria is a disease caused by a recessive gene that is localized in an autosome. Parents are heterozygous for this gene. They already have two sons with phenylketonuria and one healthy daughter. What is the probability that their fourth child will have the disease too?
- A. 50%
- B. 75%
- C. 100%
- D. 25%
- E. 0%
Hint
Each pregnancy is an independent event; work out the risk from a cross of two heterozygous carriers and ignore the earlier children.
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