Re questions of Jewish peoples (Ashkenazim, Sephardim, Samaritans etc.)
extensive Jewish DNA research work has been undertaken by Doron Behar and
colleagues and the latest paper 'The genome-wide structure of the Jewish
people' was published in Nature on 9 June 2010. An extract of the paper and
some interesting graphs can be found at http://www.tinyurls.co.uk/F5734.
[Or http://www.nature.com/nature/journal/vaop/ncurrent/abs/nature09103.html
--Mod.]
This may not answer all the questions re the similarities between various
Semitic groups but it is another huge leap.

There are a number of other papers that are available which give a picture
of the matrilineal DNA of the Ashkenazi people and one of these can be found
at http://www.familytreedna.com/pdf/43026_Doron.pdf .

As a general observation there is now so much now that is available on line
re the individual distribution of the classic Ashkenazi Jewish YDNA that we
are spoiled for choice. Start off with the Wiki entry on Ashkenazi Jews at
http://en.wikipedia.org/wiki/Ashkenazi_Jews and see where it takes you.

Martin Davis - London (UK)