Cystic fibrosis is caused by the allele f, which is completely recessive to the normal dominant allele F. Consider a couple with the genotype Ff. What is the chance that their second child will develop cystic fibrosis?
A) 25%
B) 50%
C) 75%
D) 100%
E) It depends on which alleles were inherited by their first child.

Question

Quizplus · Accepted Answer

The chance that their second child will develop cystic fibrosis is 25% because both parents are carriers (Ff), and the possible genotypes for their children are FF, Ff, Ff, and ff. Only the ff genotype results in cystic fibrosis.

Cystic Fibrosis Is Caused by the Allele F, Which Is