Researchers unmasked BRCA1 and BRCA2 as the first genetic bad actors in breast cancer. Normal copies of these two genes suppress tumors by putting the brakes on cell division or prompting cells to die when they should. Defective copies of these genes can’t control abnormal cell growth that can occur through DNA damage during ordinary body processes or outside influences like radiation. According to the American Cancer Society, genetic mutations like BRCA1 and BRCA2 account for about five to 10 percent of all breast cancers and women with them may have up to an 80 percent chance of developing the disease in their lifetime.

Continuing research on these two genes is slowly exposing the guilty tracks they make: for example, recent findings suggest that the disparate ways these genes express themselves in white and African-American women may help explain why black women develop more aggressive cancers. Scientists continue to identify additional genes that predispose women to breast cancer.