Answer:
50%
Explanation:
CF is a recessive trait. That means that an individual must have two copies of the recessive allele in their genotype in order to express the trait. That means that the parent with CF has genotype cc, while the parent who is heterozygous, and does not express the trait, has genotype Cc. Using a Punnett square to demonstrate the cross of these two parents will produce a probability of 50% heterozygous and 50% positive for CF.
