Efforts to repeat the cloning of Dolly (the sheep) have been unsuccessful. The scientists who claim to have cloned Dolly have been challenged to produce additional evidence that Dolly is really derived from an adult cell (an originally claimed), rather than a foetal cell which might have contaminated the experiment (as the sceplor suggest). Which of the following could provide evidence that Dolly was created from an adult cell, rather than a foetal cell?