Genetic studies of Jews

Genetic studies of Jews are part of the population genetics discipline and are used to analyze the ancestry of Jewish populations, complementing research in other fields such as history, linguistics, archaeology, paleontology, and medicine. These studies investigate the origins of various Jewish ethnic divisions by using DNA to investigate whether different Jewish and non-Jewish populations have shared ancestry or not. The medical genetics of Jews are studied for population-specific diseases and disease commonalities with other ethnicities.

Studies on Jewish populations have been principally conducted using three types of genealogical DNA tests: autosomal (atDNA), mitochondrial (mtDNA), and Y-chromosome (Y-DNA). Autosomal testing, which looks at the largest sets of genes within peoples' DNA, shows that Jewish populations tended to form genetic isolates – relatively closely related groups in independent communities with most in a community sharing significant ancestry. The Ashkenazi Jews form the largest such group. Mitochondrial and Y-DNA tests look at maternal and paternal ancestry respectively, via two small groups of genes transmitted only via female or male ancestors.

Studies on the genetic composition of Ashkenazi, Sephardi, and Mizrahi Jewish populations of the Jewish diaspora show significant amounts of shared Middle Eastern ancestry, as well as admixture from their host populations. Jews living in the North African, Italian, and Iberian regions show variable frequencies of genetic overlap with the historical non-Jewish population along the maternal lines. In the case of Ashkenazi and Sephardi Jews (in particular Moroccan Jews), who are closely related, the source of non-Middle-Eastern admixture is mainly Southern European. Some researchers have remarked on an especially close relationship between Ashkenazi Jews and modern Italians, Greeks, and other Southern Europeans. Bene Israel and the Cochin Jews of India, and Beta Israel of Ethiopia, resemble their local populations but also may have some near eastern lineages on the paternal side.