What Is a Risk Gene?

The genetic details that make each person unique include differences that may contribute to common health problems. When slightly different forms of a gene are known to be associated with different levels of risk for a specific health problem, that gene is called a risk gene.

A risk gene does not cause a health problem on its own. Its effect is more subtle than that. When other risk factors also are present, a risk gene can be one of the factors that tips the balance of health.

This page looks at one specific risk gene and the role it plays in type 2 diabetes. The normal function of the gene named “TCF7L2” is not completely understood, but it plays a role in the natural release of insulin. The TCF7L2 gene is an important risk factor, but it is only one of many diabetes risk genes.

The TCF7L2 gene exists in different forms. In this example, the two forms that affect diabetes risk are called "C" and "T". The "T" form of TCF7L2 is associated with a modest increase in risk. Since everyone has two copies of the gene, each person is either CC, CT, or TT. The highest risk is seen in people with two copies of the "T" form, TT. The TCF7L2 gene moves through a family just like any other gene.

View the slideshow to see one example of the "C" and "T" forms moving through a family. Then go to the next page to see the association between the TCF7L2 gene and people who have type 2 diabetes.