1997: Dolly the sheep is cloned

Scientists in Scotland have announced the birth of the world's first successfully cloned mammal, Dolly the sheep.

Dolly, who was created at the Roslin Institute in Edinburgh, was actually born on 5 July 1996 although her arrival has only just been revealed.

Dolly is the first mammal to have been successfully cloned from an adult cell. Previous clonings have been from embryo cells.

The sheep's birth has been heralded as one of the most significant scientific breakthroughs of the decade although it is likely to spark ethical controversy.

Scientists in Scotland cloned a ewe by inserting DNA from a single sheep cell into an egg and implanted it in a surrogate mother.

They now have a healthy seven-month-old sheep - Dolly - who is an exact genetic duplicate of the animal from which the single cell was taken.

DNA tests have revealed that Dolly is identical to the ewe who donated the udder cell and is unrelated to the surrogate mother.

It will enable us to study genetic diseases for which there is presently no cure

Dr Ian Wilmut, embryologist

