Question

cystic fibrosis is an autosomal recessive disease. if parents, both suffering from cystic fibrosis, have children, what is the probability that one of their children will have the disease? a 25% b 50% c 75% d 100%

Explanation:

Step1: Determine parent genotypes

Cystic fibrosis is autosomal recessive, so affected individuals have genotype aa. Both parents are affected → aa × aa.

Step2: Calculate child genotype probability

Each parent can only pass an a allele. Child must inherit a from both → aa genotype. Probability = 100%.

Answer:

D. 100%