Word: gurdon
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Dates: during 1970-1979
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...early 1960s, British Biologist John B. Gurdon took the technique a step further by replacing the nuclei of unfertilized eggs with the nuclei of cells that had differentiated into intestinal cells of young tadpoles. Some of the resulting cloned tadpoles matured into adult frogs. There have since been reports of successful cloning with nuclei from adult frog cells, but researchers have found that the best results are obtained by using the nuclei from cells of frogs in the early stages of embryonic development. The nuclei of adult animal cells are generally considered poor cloning material, possibly because many...
...Gurdon experiments still represent the high-water mark of traditional cloning technique. Researchers find that cloning mammals is a much more complicated affair. For one thing, mammalian eggs are one-tenth to one-twentieth the size of frog eggs and thus difficult to manipulate. And while tadpoles grow into frogs in a pond (and therefore easily in a laboratory tank), mammalian embryos must develop in a womb...
...eventually be able to abandon sexual reproduction entirely. That startling and perhaps unwelcome possibility has been demonstrated by Dr. J.B. Gurdon of Britain's Oxford University. Taking an unfertilized egg cell from an African clawed frog, Gurdon destroyed its nucleus by ultraviolet radiation, replacing it with the nucleus of an intestinal cell from a tadpole of the same species. The egg, discovering that it had a full set of chromosomes, instead of the half set found in unfertilized eggs, responded by beginning to divide as if it had been normally fertilized. The result was a tadpole that was the genetic...