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Biology in the Laboratory

Cloning

What was the first mammal to be successfully cloned?

The first mammal cloned from mature (somatic) cells was Dolly, a ewe born in July 1996 in Scotland—it only took 276 attempts! English embryologist Ian Wilmut (1944–) led the team of biologists that removed a nucleus from a mammary (udder) cell of a six-year-old adult ewe and transplanted it into an enucleated egg extracted from a second ewe. Electrical pulses were administered to fuse the nucleus with its new host. When the egg began to divide and develop into an embryo, it was transplanted into a surrogate mother ewe. Dolly was the genetic twin of the ewe that donated the mammary cell nucleus. On April 13, 1998, Dolly gave birth to Bonnie—the product of a normal mating between Dolly and a Welsh mountain ram. This event demonstrated that Dolly was a healthy, fertile sheep, able to produce healthy offspring.



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