There is a coordinated effort going on now at the JewishGen website, where they are using the services of Family Tree DNA to help Jewish Genealogists identify their origins.
There are many projects going on (e.g. Surname projects) which include a collection of Regional Geographical Projects, one of which is a German-Jewish SIG.
They would not be doing projects by location unless they believed the DNA could ultimately locate people. They have provided tools for each SIG to map the ancestral locations of those who had their DNA tested, versus their Haplogroup.
And latest research in Epigenetics indicates that environment does not change the genes themselves, but can affect how they are structured. This information can be detected and can potentially identify locations, habits and lifestyles of your ancestors.
Regarding your question whether the slight difference in location (Germany to Russia) for Jewish people can be detected reliably yet: It is possible, but it depends how much Jewish data has been collected for the two areas that can be related to your DNA test.
For example, the FAQ of Family Tree DNA says:
13 . Where did my ancestors come from?
We provide three tools to help
answer this question for your direct maternal line. While you are
logged in to your myFTDNA account:
- Check the haplogroup name and description on your mtDNA Results page.
This will provide background to your historic ancestry and origins.
- Check the mtDNA Ancestral Origins page. This includes places where
your DNA motif can be found today. It is influenced by more recent
- Use the myMaps tool to see a map you and your match's
most distant known ancestors and locations.
33 . What will the mtDNA Refine test tell me?
The mtDNA Refine test adds
the second hypervariable region, HVR2, to your test results. That is
the portion of your mitochondrial DNA that runs from nucleotide 00001
to nucleotide 00574. Your matches to others in the same haplogroup on
both HVR1 and HVR2 have a 50% likelihood of sharing common ancestry
with you within twenty-eight generations. That is about 700 years. If
you also share ancestry from the same location, the same village,
town, or city, then you likely share common ancestry within recent
The way to see if your wife's ancestors may have come from Germany is to join the DNA SIG for their surnames. If you find a DNA match with someone else with the same surname, and if they know their ancestors to have come from Germany, then that could indicate possible relatives in Germany and would suggest that your wife's ancestors were in Germany prior to Russia.