The BRCA1 and BRCA2 genes are part of the body’s normal mechanism to fix mistakes that occur in the DNA when cells go through normal division. However, abnormal copies of either of these genes – which are inherited from parents – do not perform naturally and as a result make a carrier more susceptible to breast and ovarian cancer.
In particular, there are three mutations (two in BRCA1 and one in BRCA2) that account for the majority of the BRCA mutations seen in persons of Ashkenazi Jewish ancestry. Women with a mutated BRCA1 or BRCA2 gene have a lifetime risk of between 36 percent and 85 percent of developing breast cancer by age 70. The average woman in the United States has about a 12 percent risk of developing breast cancer over a 90-year life span.
Women with a BRCA1 or BRCA2 gene mutation have a lifetime risk of 15 to 40 percent for developing ovarian cancer. By comparison, women who do not have a BRCA mutation have a 1.8 percent risk of developing ovarian cancer.