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GENERAL BIOLOGY Chapter 16 THE REVOLUTION IN CELL TECHNOLOGY A. CLONING The idea of cloning animals was first suggested by German embryologist Hans Spermann in 1938. The idea was to remove the nucleus from an egg cell and replace it with a nucleus from another cell. If the transplanted nucleus was from an adult the egg never fully developed. In earlier experiments, the nucleus was obtained from an advanced embryo and the egg developed into a tadpole but most died. The experiments didn’t seem to work. In 1984 Steen Willadsen succeeded in cloning a sheep in Texas. The key to his success was in using a nucleus from an earlier embryo. Other organisms followed. IAN WILMUT- July 5, 1996 the first mammal, a sheep was cloned in Scotland using an adult nuclear donor. The donor nucleus came from an adult mammary cell and the sheep, named “Dolly” was named after American Country & Western singer Dolly Parton. This was a milestone in cloning. Egg cells were removed from ewes and the nucleus removed. Mammary cells were also removed from the udder of a six-year old sheep, placed in culture and prepared for cloning. The nucleus of the mammary cell was surgically combined into the egg cells and Wilmut applied a brief electrical shock to the eggs. This allows the plasma membrane to become leaky so the contents of the mammary cell pass into the egg cell. This also jump-starts the cell and initiates cell division. As the cell divides and reaches a certain stage of development it is transplanted into the surrogate mother sheep. Approximately five months later one sheep gave birth to a lamb, Dolly. PROGRESS WITH REPRODUCTIVE CLONING: Since Dolly scientists have successfully cloned a variety of animals. This success is due to improvement in cloning techniques. Animals cloned:
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This note was uploaded on 05/19/2010 for the course BIO 101 taught by Professor Martin during the Spring '08 term at Rutgers.

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