Mutations in how many genes cause the symptoms of cystic fibrosis?
1 Answer
For the symptoms of cystic fibrosis or CF to be exhibited, the individual must have a mutation on both genes.
Explanation:
For the symptoms of cystic fibrosis or CF to be exhibited, the individual must have a mutation on both CTFR genes. This is because CF is a recessive disease, meaning a person must inherent two copies.
A person who inherited one working copy of CTFR gene and a mutation on the second CTFR gene would be a carrier of the disease, but this person would not have the disease him/herself.
In the image below, the third generation includes two individuals who are carriers, one who is not a carrier, and one who has CF. The parents of the third generation are both carriers, meaning for each child they have, each parent has a 50% chance of passing on the CF mutation. Thus, the likelihood of a child born from these parents having CF is 1/4 or (1/2)*(1/2).
