The cloning of Dolly has proved that cloning of adult animals could be accomplished. Previously, it was not known if an adult nucleus was still able to produce a completely new animal. Genetic damage or the simple deactivation of genes in cells were both considered possibly
irreversible. This however was not the case. Ian Wilmut and Keith Cambell discovered a method with which to synchronize the cell cycles of the donor cell nucleus and the host egg cell cytoplasm. Without synchronized cell cycles, the donor nucleus would not be in the correct state for the host egg to accept it. The donor cell was forced into the Go stage of the mitotic cell cycle by starving the cells. When the nucleus enters the egg cytoplasm, egg proteins "re-program" the chromosomes in the nucleus. The dividing embryo is transferred into the oviduct of a surrogate mother sheep. The embryo continues to divide and then implants in the uterine wall.
The Cloning of Dolly
