The genome-wide structure of the Jewish people
From a study published in Nature, 08 July 2010: “… we use high-density bead arrays to genotype individuals from 14 Jewish Diaspora communities and compare these patterns of genome-wide diversity with those from 69 Old World non-Jewish populations, of which 25 have not previously been reported. These samples were carefully chosen to provide comprehensive comparisons between Jewish and non-Jewish populations in the Diaspora, as well as with non-Jewish populations from the Middle East and north Africa. …”
My conclusion: Most Jewish communities are highly admixed with the local communities.