"Signatures of founder effects, admixture, and selection in the Ashkenazi Jewish population." Proceedings of the National Academy of Sciences of the United States of America (PNAS) 1 (September 14, 2010): pages 16222-16227. Among the comparative populations were 1705 continental Europeans and 1251 European-Americans.
[...] High linkage disequilibrium can come either from an isolated population (for example, an island whose residents are all descendents of shipwreck survivors) or the relatively recent mixture of separate populations.
Bray and his colleagues did find evidence of elevated linkage disequilibrium in the Ashkenazi Jewish population, but were able to show that this matches signs of interbreeding or 'admixture' between Middle Eastern and European populations.
Order a DNA kit from FTDNA's headquarters in the USA This page collects Y-DNA and mt DNA data and analysis related to traditionally Rabbinical Jewish populations of the world, including: Ashkenazim (Jews of Northern and Eastern Europe) • Sephardim (Spanish and Portuguese Jews) • Mizrakhim (Middle Eastern Jews) • Italkim (Italian Jews) • Caucasian Mountain Jews (Dagestani and Azerbaijani Jews) • Georgian Jews • Indian Jews • North African Jews • Yemenite Jews • Ethiopian Jews Steven M. However, paradoxically we also found higher genetic diversity, a sign of an older or more admixed population but not of a long-term isolate.
Also used for comparison were 3 Middle Eastern populations: Palestinian Arabs, Druze, and Bedouins.
The genomic analysis also provided information about selection pressures on mutations prevalent in the Ashkenazi Jewish population, such as those leading to conditions like Tay-Sachs disease or mutations in cancer susceptibility genes like BRCA1.
[...]" Gil Atzmon, Li Hao, Itsik Pe'er, Christopher Velez, Alexander Pearlman, Pier Francesco Palamara, Bernice Morrow, Eitan Friedman, Carole Oddoux, Edward Burns, Harry Ostrer.The researchers were able to estimate that between 35 and 55 percent of the modern Ashkenazi genome comes from European descent.[...] He adds that his group's analysis agrees with a recently published study from New York University and Albert Einstein College of Medicine, and supports estimates of a high level of European admixture, accounting for up to half of the genetic make-up of contemporary Ashkenazi.Additionally, we applied extended haplotype tests to determine whether positive selection can account for the level of AJ-prevalent diseases.We identified genomic regions under selection that account for lactose and alcohol tolerance, and although we found evidence for positive selection at some AJ-prevalent disease loci, the higher incidence of the majority of these diseases is likely the result of genetic drift following a bottleneck.The IBD segment sharing and the proximity of European Jews to each other and to southern European populations suggested similar origins for European Jewry and refuted large-scale genetic contributions of Central and Eastern European and Slavic populations to the formation of Ashkenazi Jewry.