Understanding the Genetics Behind Cystic Fibrosis

Cystic fibrosis occurs due to an inherited genetic mutation. But understanding the specifics can get a little confusing. How do perfectly healthy parents end up with a child with cystic fibrosis?

In this article, we are going to tackle the basics of genetics and their role in the inheritance of cystic fibrosis.

Genes, what they do for us, and how they affect the diseases or physical attributes we end up with

First of all, we need a basic lesson in genetics and how they are passed on from generation to generation. Basically, our DNA is a blueprint of how our body is supposed to develop, starting from when an egg and sperm meet in fertilization. As a small fetus, the unborn child grows based on a roadmap already pre-determined by genetic code inherited from mom and dad. Genes have everything to do with how our body functions and how we look.

Genes are inherited and they determine what you end up looking like, as well as how your body will function

Genes are packaged into more compact bodies known as chromosomes. Humans have 23 pairs of chromosomes, and each pair contains the same types of genes. Every gene type has 2 paired alleles, one inherited from mom and the other inherited from dad. This double copy is what allows us to survive potentially malfunctioning genes due to chance mutation or inheritance. If you get a faulty gene from one parent, hopefully, the other parent gives you a normal one to override it.

You need two mutated genes in order to get cystic fibrosis

In cystic fibrosis, both alleles of a chloride channel protein are mutated, resulting in a malfunctioning chloride channel. This is why patients with cystic fibrosis suffer the symptoms that they have - thick respiratory secretions, pancreatic malfunction, digestive issues, and other complications. The thick respiratory secretions result in more frequent lung infections due to poor clearance of lung debris, and chronic infections can lead to permanent damage and scarring of the actual lung tissue. The pancreas normally secretes digestive enzymes to help us digest fats, and the release of these enzymes also depends on the chloride channel. Without it, cystic fibrosis patients have very thick pancreatic secretions resulting in the poor release of these digestive enzymes. As a result, patients get poor digestion and malnutrition, as well as damage to the pancreas itself.

Cystic fibrosis is a recessive disease, meaning you need to inherit a bad allele from both your parents

Because you need both alleles to be mutated in order to have cystic fibrosis, it's referred to as a recessive disease. If you are able to have at least one functioning allele for this chloride channel inherited from your parents, then you are safe from cystic fibrosis. A person who is healthy but has one mutated allele is known as a carrier because they do have a risk of giving this faulty allele to their children. If two carrier parents have a child, that child has the risk of inheriting both the faulty alleles, one from each parent.

Read on to learn more about the genetic risk associated with cystic fibrosis.