R’ Moshe writes in Igros Moshe Even Haezer 4:9: ?????? ??????? ?????? ???? ?? ????? which might be similar to or the source for what Mod 42 and Sam2 said. (R’ Moshe is talking about Amram and Yocheved but there’s no reason to assume that it wouldn’t apply to the shevatim as well.)
http://www.hebrewbooks.org/pdfpager.aspx?req=921&pgnum=15
Also, Writersoul, in answer to one of your questions on the article about mitochondrial DNA, namely:
Rachel and Leah were sisters (same mother) so they would have the same mtDNA
I will point out that Rachel and Leah may not have had the same mother.
Although there are sources that they did have the same mother, for instance Seder Olam Rabba Perek 2: ????? ??? ???? ???? ???? ?”? ?”? ???? ?????? and Sefer Hayashar (Parshat Toldot):
?????? ?’ ?? ????? ??? ??? ???? ?? ???? ???? ??? ???? ??????
http://www.hebrewbooks.org/pdfpager.aspx?req=40009&st=&pgnum=97&hilite=
R’ Moshe in the aforequoted teshuvah, writes:
?? ??? ????? ??? ??? ????? ?? ??? ??? thus leaving open the possibility that they did not have the same mother and I have seen quoted that the Tiferes Shlomo says that they had different mothers, though I have not managed to find it inside.
So perhaps the study can be used to prove which position is correct (although we would first have to demonstrate the reliability of the study).