Chapter 28, Problem 30RQ

Zoe has cystic fibrosis. Which of the following is the most likely explanation?

1. Zoe probably inherited one faulty allele from her father, who is a earner, and one normal allele from her mother.
2. Zoe probably inherited one faulty allele from her mother, who must also have cystic fibrosis, and one normal allele from her father.
3. Zoe must have inherited faulty alleles from both parents, both of whom must also have cystic fibrosis,
4. Zoe must have inherited faulty alleles from both parents, both of whom are earners.