Ashkenazi jews who make up 80% of jewish population come from Europe, DNA studies prove this.
PC1 distinguished Northern and Southern European and Jewish and Middle Eastern populations. Along this axis, Europeans were closest to Ashkenazi Jews, followed by Sephardic, Italian, Syrian, and Middle Eastern Jews. Of the European populations, the Northern Italians showed the greatest proximity to the Jews, followed by Sardinians and French (Figure 1B), an observation that was confirmed by FST (Table 1). Also along this axis, the Adygei, a Caucasian population, showed proximity to the Ashkenazi Jews...
...Two major differences among the populations in this study were the high degree of European admixture (30%–60%) among the Ashkenazi, Sephardic, Italian, and Syrian Jews and the genetic proximity of these populations to each other compared to their proximity to Iranian and Iraqi Jews...
...recorded mass conversions led to 6 million people practicing Judaism in Roman times or up to 10% of the population of the Roman Empire. Thus, the genetic proximity of these European/Syrian Jewish populations, including Ashkenazi Jews, to each other and to French, Northern Italian, and Sardinian populations favors the idea of non-Semitic Mediterranean ancestry in the formation of the European/Syrian Jewish groups...
...Admixture with local populations, including Khazars and Slavs, may have occurred subsequently during the 1000 year (2nd millennium) history of the European Jews....
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3032072/?tool=pmcentrez