Specific gene alterations in BRCA1 or BRCA2 genes have been identified in different ethnic groups.
Among individuals of Ashkenazi Jewish descent, researchers have found that about 2.3% (23 out of 1,000 persons) have an altered BRCA1 or BRCA2 gene. This frequency is about 5 times higher than that of the general population. However, it is still not known whether the increased frequency of these BRCA1 and BRCA2 gene alterations is responsible for the increased risk of breast cancer in Jewish populations, compared with non-Jewish populations.
Other ethnic and geographic populations, such as the Norwegian, Dutch, and Icelandic people, also have a higher rate of certain genetic alterations in BRCA1 and BRCA2.