In a second study, Dr. Skorecki and associates gathered more DNA samples and expanded their selection of Y chromosome markers. Solidifying their hypothesis of the common ancestor of Cohanim, they found that a particular array of six chromosomal markers were found in 97 of the 106 Cohanim tested. The chances of these findings happening at random is greater than one in 10,000. Processor Hammer was recently in Israel for the Jewish Genome Conference. Other Y chromosomes can enter the Jewish gene pool through conversion or through a non-Jewish father.
Jewish status is determined by the mother.
Tribe membership follows the father's family line. Wider genetic studies of diverse present day Jewish communities show a remarkable genetic cohesiveness. Jews from Iran, Iraq, Yemen, North Africa and European Ashkenazim all cluster together with other Semitic groups, with their origin in the Middle East. A common geographical origin can be seen for all mainstream Jewish groups studied. Researchers compared the DNA signature of the Ashkenazic Jews against those of Turkish-derived people, and found no correspondence.