 Dolly, however, was not 100% genetically identical to the donor animal. Genetic material comes from two sources: the nucleus and the mitochondria of a cell. Mitochondria are organelles that serve as power sources to the cell. They contain short segments of DNA. In Dolly’s case, her nuclear DNA was the same as the donor animal; other of her genetic materials came from the mitochondria in the cytoplasm of the enucleated oocyte. For the clone and the donor animal to be exact genetic copies, the oocyte too would have to come from the donor animal (or from the same maternal line – mitochondria are passed on by oocytes).