Cystic Fibrosis (CF)is Caused by a Recessive Allele

question 45

Multiple Choice

Cystic fibrosis (CF) is caused by a recessive allele.A child has CF,even though neither of his parents has CF.This couple also has a child who does not have CF.What is the probability the unaffected child is heterozygous?

• A)2/3
• B)1/3
• C)1/2
• D)3/4
• E)1/4

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