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Unformatted text preview: an egg cell. Electric shock opens cell membranes and triggers cell division. The embryo then begins to develop in vitro and is implanted into the surrogate mother. The pregnancy was five months long and a lamb that was genetically identical to the sheep from which the mammary cell was extracted from. Why Cloning Fails Normal development depends on precise genomic imprinting. This chemical reprogramming of the DNAtakes months for sperm and years for eggs. During cloning the reprogramming must take minutes. The reprogramming job is not done nearly as well because of the time difference. Human cloning will not be practical until scientists figure out how to reprogram a donor nucleus, as occurs in the DNA of sperm or eggs in our bodies. (Raven 7 th Edition Biology)...
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- Spring '08