The “Uniqueness” of Ashkenazi Jewish Ancestry is Important for Health

Editor’s note: Pending an FDA decision, 23andMe no longer offers new customers access to health reports referred to in this post. Customers who purchased prior to November 22, 2013 will still be able to see their health reports, but those who purchased after that time will not. Those customers will have access to ancestry information as well as access to their uninterpreted raw data.

Ashkenazi Jews are one group that fall under the umbrella of “European”, but it’s clear from numerous studies that they’re genetically unique and distinct from the European population at large. Most people with Ashkenazi ancestry trace their DNA to Eastern and Central Europe, but also have Middle Eastern ancestry, which is just one reason for their genetic “uniqueness”.

Genetic Variation Between and Within Populations

It’s clear that people with European ancestry are genetically distinct from those of Asian or African descent, but what’s less obvious is that genetic variation also exists within European groups. In these plots from a study by Elimear Kenny, you can see the genetic variation between major ancestral groups (left) and within a population (right). Jewish groups fall into the European cluster on the left, but people with Ashkenazi ancestry (blue) form a unique cluster that is largely distinct from Caucasian (CEU; green) and other Jewish populations (various colors) on the right. Individuals who are part Ashkenazi fall in between the Caucasian and Ashkenazi clusters.

The challenging history of Jewish groups has also contributed to their genetic uniqueness. During the Jewish Diaspora — or migration of Jewish people from the Middle East to other parts of the world — the vast majority of Jewish individuals married and raised families within their faith. Many generations later this means that Ashkenazi Jews can appear more genetically related than they actually are.

This genetic isolation has had important implications for health. People with Ashkenazi ancestry are more likely to carry genetic factors that cause single-gene recessive Mendelian disorders where you need two bad copies of a gene to get the disease. Examples include Gaucher disease, Canavan disease, and Tay-Sachs disease. Because of this higher likelihood, screening for these genetic variants in prospective parents is standard practice for Jewish individuals starting families.

(23andMe tests for most mutations routinely screened in the Ashkenazi Jewish population for these conditions).

23andMe customers can learn about their ancestry and view their results for Gaucher disease, Canavan disease, and Tay-Sachs disease in their account.

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A number of multi-gene conditions (or those caused by genetic variation in a handful of genes) are also more common in people with Ashkenazi ancestry. One example is Crohn’s disease, which people with Ashkenazi ancestry are two to four times as likely to develop compared Europeans in general. Although it’s not yet clear why the rates are higher in this population, it’s likely that genetic factors specific to individuals with Ashkenazi ancestry play a role.

Knowing about your ancestry can teach you about your family’s heritage and your risk for disease — and more knowledge means more informed decisions.

May is Jewish American Heritage Month. Check back later to read about genetic risk factors for Crohn’s disease that appear to be specific to people with Ashkenazi Jewish ancestry. You can also read about uncovering Jewish ancestry in guest posts by 23andMe’s Ancestry Ambassadors, Tim JanzenCeCe Moore and Andrea Badger.