1 out of 40 Ashkenazi Jewish women have a BRCA 1 or BRCA 2 gene mutation which gives them a 33%-50% risk of developing breast cancer by age 50 and 56%-87% by age 70. Men carrying the gene mutation have a slightly higher incidence of cancers but, importantly, can pass it on to their daughters. A simple blood test will tell you if you have a BRCA 1 or BRCA 2 gene mutation.