Genetics and Evolution

What was the first mammal to be successfully cloned?

The first mammal cloned from adult cells was Dolly, an ewe born 0n July 5, 1996. Dolly was born in a research facility in Scotland. Ian Wilmut (1944–) led the team of biologists that removed a nucleus from a mammary cell of an 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 demonstrates that Dolly was a healthy, fertile sheep, able to produce healthy offspring. Dolly was euthanized on February 14, 2003, because she had severe arthritis and a progressive lung disease that was caused by the retrovirus JSRV.


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