Dolly was the first mammal cloned from a cell from an adult animal. She was derived from cells that had been taken from the udder of a 6-year old Finn Dorset ewe and cultured for several weeks in the laboratory. Individual cells were then fused with unfertilised eggs from which the genetic material had been removed. Two hundred and seventy seven of these reconstructed eggs' - each now with a diploid nucleus from the adult animal - were cultured for 6 days in temporary recipients. Twenty nine of the eggs that appeared to have developed normally to the blastocyst stage were implanted into surrogate Scottish Blackface ewes. One gave rise to live lamb, Dolly, some 148 days later.
Dolly was born on 5 July 1996.