One in 40 women of Ashkenazi (French, German, and East European) Jewish descent carry the BRCA1 and BRCA2 (breast cancer) gene, which is significantly higher than in the general population where only 1 in 500 to 800 people carry the gene.
Bellenir, Karen, ed. 2009. Breast Cancer Sourcebook. 3rd ed. Detroit, MI: Omnigraphics.