Earlier in this blog, I indicated that DNA rearrangements and deletions during cellular differentiation may make nuclear compartments unavailable to be used for cloning specific kinds of stem cells because all of the DNA is not there. If this is true, then, such cells could never be used to clone whole animals. However, examples of adult animals being cloned from single adult cells abound in the literature as shown in this recent video: Mice cloned from a drop of blood.
So how can this be possible if some of the DNA is missing from these adult cells? The short answer is that it would be impossible. So, how do we reconcile this paradox? First of all, most cloning experiments are highly inefficient, meaning that only a few percent of the attempts are ever successful. Why so? Again, the short answer is that most of these cells are adult stem cells that are in fact missing some of the DNA required to make a complete animal. This is why most of them fail. The few that do succeed must actually be true germ cells that exist outside of the sex organs, much like apical meristem in plants.