Members of the Jewish community who trace their roots to Central or Eastern Europe are known as Ashkenazi Jews. Although today members of this community are found around the world, Ashkenazi Jews for centuries were a geographically isolated population. The isolation experienced by this population means its members can trace their ancestry back to a small number of members known as “founders.” Over time, the genetic traits of these early Ashkenazi “founders” have been passed down through generations, including a greater frequency of BRCA1 and BRCA2 gene mutations.
The mutations in BRCA1 and BRCA2 that occur more frequently in Ashkenazi Jews are called "founder genes". About one out of every 40 individuals of Ashkenazi Jewish ancestry have a mutation in the BRCA1 or BRCA2 gene, as compared to one out of every 800 members of the general population, according to the US Center for Disease Control.
The Ashkenazi women carrying founder genes have a lifetime risk of between 36 percent and 85 percent for developing breast cancer and a lifetime risk of 15 to 40 percent for developing ovarian cancer. Just as Ashkenazi women have an increased risk of inheriting a mutated BRCA gene from one or both of their parents, so do Ashkenazi men. Men who inherit these genes have approximately a 6 percent risk for developing breast cancer during their lifetime. That risk is 80 percent greater than the lifetime risk of men without a mutated BRCA gene. Men with mutated BRCA genes may also be three to seven times more likely than average to develop prostate cancer. Other cancer risks, such as cancer of the skin or digestive tract, may also be somewhat higher among both sexes with these mutations, but the risk of these cancers is much lower.
Large studies in Canada, Israel, and the United Kingdom indicate that more than half of Ashkenazi women who carry the mutation do not qualify for genetic testing on the basis of family history.
Research has shown that in the Bahamas, a large portion of women with breast cancer carry one of seven founder mutations in the BRCA1 or BRCA2 gene.
High Risk Ethnic Groups
Other population groups around the world that are at increased risk of BRCA mutations include people of Norwegian, Polish, African, Dutch, East Indian and Icelandic descent.