Question

Mutations in CFTR are recessive. If two people that are genetic carriers of Cystic Fibrosis (CTFR/ctfr) have children together, what percentage of children would develop cystic fibrosis?

a) 0%
b) 25%
c) 50%
d) 75%

Answer 1

With two carriers of Cystic Fibrosis, each child has a 25% chance of developing cystic fibrosis as it is an autosomal recessive condition.

Step-by-step explanation:

If two genetic carriers of Cystic Fibrosis (CFTR/ctfr) have children together, the percentage of children that would develop cystic fibrosis is 25%. This is calculated using a Punnett square, which shows how the alleles from each parent can combine in their offspring.

Given that cystic fibrosis is an autosomal recessive condition, a child must inherit two copies of the recessive allele (ctfr) from both parents to express the disease.

According to the Punnett square, with both parents being carriers (Ff), there is a 25% chance (probability) for each child to receive the affected genotype (ff), therefore developing cystic fibrosis. In contrast, there is a 75% chance (probability) for a child to not be affected by the disease; this includes a 50% chance of being a carrier (Ff) and a 25% chance to have the normal genotype (FF).