On 2008.04.03, Robin Altwarg <robin@...> asked:

[...]If my
cousin and I had our mtDNA tested would we be able to confirm or
disconfirm whether we share a great-grandmother? If so, do we have
to take a particular type of test?

Robin, if both you and your cousin are descended through all-female
maternal lines >from either one of your great-grandfather's wives,
the mtDNA test will make the distinction you're seeking. You can use
any of the basic mtDNA tests offered by commecial laboratories, or
by the non-profit National Geographic Society Genographic Project.

If your samples don't match, you'll know for sure you had different
great grandmothers. If they match exactly, you probably share same
great gfrandmother, but there's an outside possibility you had
different ones, each descended in a separate all-maternal line from
a more distant common ancestor. The basic mtDNA test can't eliminte
that possibility.

Donn Devine
Wilmington Delaware