Most people who develop breast or ovarian cancer have no history of the disease in their family. In fact, only 5 to 10 percent of all breast and ovarian cancers are caused by inherited genetic factors. These rare cases typically result from inherited mutations in either the BRCA1 or BRCA2 gene. BRCA1 and BRCA2 are called tumor suppressor genes, because they control cell growth. BRCA1 is located on chromosome 17, and BRCA2 on chromosome 13. Scientists believe BRCA1 and BRCA2 work by fixing damaged or broken DNA. Women who inherit a mutated copy of the BRCA1 or BRCA2 gene accumulate broken and deformed chromosomes, and therefore have a greater chance of accumulating mutations that will lead to uncontrolled cell growth and cancer. Men who inherit the defective genes are also more likely to develop breast and/or prostate cancer. (Yes, men can get breast cancer.)