Cystic fibrosis is a deadly disease of the lungs and digestive system. It is inherited as a recessive trait. How can two healthy parents have a child with cystic fibrosis?
The parents may possess the recessive trait. Let’s say both parents have the allele of Aa, where ‘a’ is the trait for cystic fibrosis, there is a chance that their child will posses the allele ‘aa’, meaning they would have the disease.
