Each sample from the earlier series was matched with the most similar one from the later series, and they were placed in identical cell cultures to see which would multiply the most.

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Sir Ian and his team fused the genetic information from an adult sheep cell nucleus with an egg cell to form an embryo that developed into a genetically identical copy of the original adult.

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These work by binding chemically to that enzyme's active site to inhibit its action. (Protease cuts the raw chain of virus protein produced by a subverted cell into functional molecules.) However, the mechanism is not quite identical.

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