Cloning, as we are speaking here seems to be mainly concentrated on the idea of reproducing a being. To date much of the cloning attempts have been, like the first reported case of Dolly, the sheep, with the cloning of adult female animals. It is amazing that the people doing cloning experiments did not remember their basic mammalian biology and realize that it is impossible to clone a female and get an exact duplicate, unless the original being were herself a clone.
The explanation is this, any female is made up of a mosaic of two different kinds of cells because the XX chromosome pairs can be said to "compete for dominance" with the "losing X" taking a different role. As a mature cell will be from but one part of the mosaic, the resulting female clone will not be a duplicate of the original but a creation of approximately half of the original.
If you want to understand this easily, think of the Calico Cat, whose pretty coat is due to this XX-competition effect. Cloning a Calico Cat could produce almost any color of cat, but not another Calico.
It's no wonder Dolly died quite young, she lacked the protection of the double mosaic.
It is strange that, in so far as I know, no one has ever noted the above problem in any literature about cloning. If there is any literature reference found, please cite it! Thanks.