Forty percent of women carry a gene which can double the risk of breast cancer and is responsible for nearly thirty percent of all breast cancer cases. The gene, CYP17, controls estrogen production and influences girls as they go through puberty. Researchers at the University of Southern California presented this information to the American Cancer Society on March 24th and signaled a different trend in breast cancer research. Most researchers have focused on BRCA1 and BRCA2 genes that substantially increase the risk of breast cancer, but that are very rare. These researchers were looking for genes that were more common and found them in CYP17, although this gene was not as determinative in contracting the disease.