If a parent has cystic fibrosis, will his or her child inherit the disease?

We all have pairs of genes in our DNA makeup. We inherit one set of genes from our mother and the other set from our father. Cystic fibrosis is a recessive genetic condition. This means that you must have two defective genes, one from your mother and one from your father, to inherit the condition. If you have only one defective gene from one parent, you are a carrier of the condition. Carriers do not show any symptoms of cystic fibrosis but they can pass on the defective gene to their offspring. Therefore, the chance of a child having cystic fibrosis depends on the genetic makeup of the parents [source: PubMed Health].

So, if one parent has two defective genes (and hence has cystic fibrosis) and the other parent has one defective gene and one healthy gene, an offspring has no chance of inheriting cystic fibrosis. An offspring in this scenario, however, has a hundred percent chance of being a carrier, since the child will inherit one defective gene from the parent that has cystic fibrosis. If, however, one parent has two defective genes and the other parent has one defective gene, a child has a 50 percent chance of inheriting the condition [source: Lucille Packard Children's Hospital at Stanford].

Cystic fibrosis is most common in Caucasians of northern European descent. The condition occurs in approximately one out of every 3,000 live births. About 25 percent of this ethnic group is carriers for the condition. If cystic fibrosis occurs in your family, you may want to consult a genetic counselor for genetic testing. Genetic testing simply involves a cotton swab of your inner cheek. Most genetics labs test for 30 to 100 different mutations of the cystic fibrosis gene with very good accuracy [source: Lucille Packard Children's Hospital at Stanford].