Cystic fibrosis is caused by the allele f, which is completely recessive to the normal dominant allele F. Consider a couple who both have the genotype Ff. What is the chance that their first child will develop cystic fibrosis?
A) 0%
B) 25%
C) 50%
D) 75%

Question

Quizplus · Accepted Answer

Both parents carry one copy of the recessive allele f but do not have cystic fibrosis. Therefore, there is a 25% chance that their offspring will inherit two copies of the recessive allele (f) and develop cystic fibrosis. The possible genotypes for their offspring are FF, Ff, and ff with a 25% chance of each genotype.

Cystic Fibrosis Is Caused by the Allele F, Which Is