5 juill. 1996 - Dolly the sheep cloned

Description:

Dolly, female Finn Dorset sheep that lived from 1996 to 2003, the first clone of an adult mammal, produced by British developmental biologist Ian Wilmut and colleagues of the Roslin Institute, near Edinburgh, Scotland. The announcement in February 1997 of Dolly’s birth marked a milestone in science, dispelling decades of presumption that adult mammals could not be cloned and igniting a debate concerning the many possible uses and misuses of mammalian cloning technology.
The concept of mammalian clones, even humans, was not new at the time of Dolly’s birth. Among mammals, naturally occurring genetic clones, or individuals genetically identical to one another, had long been recognized in the form of monozygotic (identical) twins. Unlike Dolly, however, such clones are derived from a single zygote, or fertilized egg, and thus they are clones of one another, rather than clones of another individual. Moreover, clones had been generated previously in the laboratory, but only from embryonic cells that were either undifferentiated or only partially differentiated. In animals, the production of clones from fully differentiated (adult) cells (e.g., skin or muscle cells) had been carried out successfully only in lower species, such as frogs.

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