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A clone is a group of organisms that are genetically identical. Most clones result from asexual reproduction, a process in which a new organism develops from only one parent. The one process of cloning, called nuclear transfer, replaces the nucleus of an immature ....

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.... culture containing hormones. The first cloning of animal cells took place in 1964. John B. Gurdon took the nuclei from tadpoles and injected them into unfertilized eggs. The nuclei containing the original parents’ genetic information had been destroyed with ultraviolet light. When the eggs were incubated, Gurdon discovered that only 1% to 2% of the eggs had developed into fertile adult toads. The first successful cloning of mammal was achieved nearly twenty years later. Scientists from Switzerland and the U.S. successfully cloned mice using a method similar to Gurdon’s, but required one extra step. After the nucleus was taken from the embryos o ....