Table of Contents Information on Cystic Fibrosis? How Common Is Cystic Fibrosis? Cystic Fibrosis Symptoms Suspecting a Child May Have Cystic Fibrosis Cystic Fibrosis Symptoms & Diagnosis What Makes Cystic Fibrosis a Genetic Disease? Cystic Fibrosis Treatment How the Gene Mutation Causes Cystic Fibrosis Gene Therapy as a Cystic Fibrosis Treatment Detecting Cystic Fibrosis in an Unborn Baby Can Cystic Fibrosis Be Prevented? How Patients and Their Families can Cope Keeping on Top of Your Conditio

What Makes Cystic Fibrosis a Genetic Disease?

Every human being has 46 chromosomes, 23 inherited from each parent. Because each of the 23 pairs of chromosomes contains a complete set of genes, every individual has two sets (one from each parent) of genes for each function. In some individuals, the basic building blocks of a gene (called base pairs) are altered (mutated). A mutation can cause the body to make a defective protein or no protein at all. The result is a loss of some essential biological function and that leads to disease. Children may inherit altered genes from one or both parents.

Diseases such as cystic fibrosis that are caused by inherited genes are called genetic diseases. In CF, each parent carries one abnormal cystic fibrosis gene and one normal CF gene but shows no evidence of the disease because the normal cystic fibrosis gene dominates or "recesses" the abnormal CF gene. To have CF, a child must inherit two abnormal genes-one from each parent. The recessive CF gene can occur in both boys and girls because it is located on non-sex-linked chromosomes called autosomal chromosomes. CF is therefore called an autosomal recessive genetic disease.

The inheritance patterns for the cystic fibrosis gene are shown in the accompanying diagram. Each child, whether male or female, has a 25 percent risk of inheriting a defective gene from each parent and of having CF. A child born to two CF patients (an unlikely event) would be at a 100 percent risk of developing CF.

Cystic Fibrosis Pictures: Recessive Inheritance The presence of two mutant genes (g) is needed for CF to appear. Each parent carries one defective gene (g) and one normal gene (G). The single normal gene is sufficient for normal function of the mucus glands, and the parents are therefore CF-free. Each child has a 25 percent risk of inheriting two defective genes and getting CF, a 25 percent chance of inheriting two normal genes, and a 50 percent chance of being an unaffected carrier like the parents.