Difficulty: Medium
Average Score: 73%
Full-length
Cystic fibrosis is transmitted as an autosomal recessive trait. This means that:
Correct answer
D
Rationale
Cystic fibrosis is not an X-linked or sex-linked disease. The only characteristic on the Y chromosome is the trait for hairy ears. Both parents do not need to have the disease but must be carriers. If a trait is recessive, two genes (one from each parent) are necessary to produce an affected child.