Jewish people have some unique Genetic Markers on the Y-Chromosome, in particular the descendents of Aaron (the Kohen groups)
There is a tribe in India that is suspected of being one of the 10 Lost Tribes of Israel (the Menasheh tribe).
Authorities are planning on performing some Genetic Tests.
Under the Law of Return...any person officially recognized as being Jewish can become a
Citizen of Israel.
Below is a link to a short article and good size video..
The video has some graphical images
Some History on the Lost Tribes
Tribes of Israel