What Are Genes?

Genes carry the information that determines our traits, which are features or characteristics we inherit from our parents — like eye color, height, and the color and texture of our hair. They also determine things like whether babies will be male or female, the amount of oxygen blood can carry, and the likelihood of getting some diseases.

Scientists believe that every human has about 20,000 to 25,000 genes. If even one of these genes is missing or has changed (mutated), it can cause a disease. Sometimes a mutation is inherited, just like curly hair or brown eyes. Others happen for no known reason, without having been passed on by a parent. 

What Is Gene Therapy?

Gene therapy involves using genes to fight or prevent diseases. It might mean replacing a gene that isn’t working properly, adding a "good" gene into a person who has a disease, or blocking a gene that is causing a problem.

Gene therapy is promising, but for now is only used to treat a few diseases that have no other effective treatments. Many types of gene therapy are still being studied to see how safe they are, and if they can work to treat or prevent diseases. This process is slow because experts have to make sure that the benefits are worth the risks.

With time, gene therapy has the potential to prevent and treat many diseases.