Patients with a genetic condition known as cystic fibrosis struggle with symptoms such as lung and digestive problems. At the cellular level, the cells of patients with the disease do not transport water or other materials out of the cell efficiently. Therefore, patients’ cells have a build up of water and other substances inside the cell. Which of the following best describes how cystic fibrosis impacts cells?

One pair of chromosomes includes a gene called the cystic fibrosis transmembrane conductance regulator (CFTR) gene. This gene is large and complex — in fact, more than 1,000 different CF-related mutations have been identified.

In most people, the CFTR gene helps regulate the flow of salt and fluid in and out of cells. But if there is a mutation in this gene, chloride, a component of salt, gets stuck inside the cells and a thick, sticky mucus starts to build up inside the body.

Explanation: