I am interested in stem cell research, and one of the methods used in obtaining valid embrionic cells was using a rabbit egg, which had its nucleus replaced with that of a human epitelial cell, then you would obtain a clone embrio which could be used to harvest totipotent stem cells. I know that most of the DNA is contained by the nucleus but there is also extranuclear DNA contained by plastides – mithocondrias. So, if the nuclear DNA was human the mithocondrial DNA was that of a rabbit. I know that mithocondria are basically the same, but mutations occur and mithocondrial DNA doesnt’ suffer repairals like nuclear DNA so I thought that there must be differences between animal and human mithocondria (evolution is valable for them too). My question is are rabbit mithocondria better than human ones, or more general are some mithocondria better than others? I thought that small mammals with intense metabolism have more mithocondria or theirs produce a higher quantity of oxido-reducing enzymes. Maybe you could help me in finding the answer at this question, especially biostudent84 since you are working also with stem cells.