Our bodies are made up of a complex mix of chemicals. Most of the important functions in the body are performed by chemicals called proteins. Each protein has a specific function. For example, some proteins help cells in the body to keep their shape, while others allow them to grow and divide normally.

Genes are the "blueprints" for making proteins. Each cell in the body has a complete set of these blueprints (about 25,000 different genes). Genes are made of a substance called DNA, which sits in long strands called chromosomes in the middle (nucleus) of each cell.

We inherit our genes from our parents. Genes are responsible for many of the traits we can easily see, such as the color of our eyes and whether we have curly hair. But genes can have more subtle effects as well, such as on our tendency to get diseases such as cancer.

Sometimes changes (mutations) in genes are inherited from our parents, and sometimes genes change during our lifetime, such as when a cell is exposed to something that damages its DNA (like radiation or cigarette smoke). These gene changes, in turn, affect the proteins they code for. If a protein is normally involved in keeping the cell's growth in check, a faulty protein may lead to unwanted growth.

Researchers now believe that for most cancers to develop, it probably requires changes in several of our genes. These changes can either be inherited from our parents or acquired during our lives.

To learn more about genes and how they relate to cancer, please see the American Cancer Society document, Oncogenes and Tumor Suppressor Genes.

Revised: 05/24/2007