Dolly

The Roslin Institute creates Dolly using nuclear transfer (fusion) (link to doc 1). By using a frozen adult cell to create a successful clone, which scientists earlier believed to be biologically impossible, the institute causes a worldwide sensation.

It took 277 attempts before Dolly was cloned.

Polly

Polly is different from Dolly in that she was cloned using foetal cells and has an extra human gene. Her extra human gene means that when Polly produces milk she will also produce a special protein (one that helps blood clotting), which can be isolated and used for pharmaceutical purposes.

George and Charlie

George and Charlie, similar to Polly, too have an additional human gene, which makes them produce human serum albumin (used in blood transfusions) in their milk.

Cumulina and her family of cloned mice

The nucleus from a cumulus cell (body cells that nourish the ripening egg) is injected into an egg that has been previously emptied of its genetic material. The egg's development is then activated.

274 attempts at cloning only produced three mice, two of which died immediately, with Cumulina as the sole survivor. The cloning was repeatedly done again, and by November 1998, more than 60 clones had been created.

This is remarkable as it suggests that cloning can become routine. However, viable clones are generated only once or twice in every hundred attempts.

Tetra

Splitting a very early embryo consisting of only eight cells into four pieces created the rhesus monkey, Tetra. This process is called artificial twinning (link to doc 1) and is different from nuclear transfer. The split embryos were then nurtured into new embryos. Tetra has both a mother and a father and is a clone of neither, but is rather an artificial quadruplet. The researchers made 368 embryos by splitting 107 embryos into two or four pieces. They achieved 4 pregnancies in 13 tries. Only Tetra survived.

Xena

Created differently from the five pigs by PPL Therapeutics, which were cloned by nuclear transfer (fusion), Xena is cloned using microinjection. This is similar to the method used by the University of Hawaii to clone mice.

Researchers tried 110 times before Xena was born.

Noah

Noah was cloned using nuclear transfer (microinjection), using an adult gaur's skin cell. Noah died from scours, chronic diarrhoea in livestock caused by intestinal infection. Some researchers question whether the cloning process may have played a part in Noah's death, as scours is not the most common cause of death in newborn calves.

Cumulina and her cloned family of mice.The original mouse is on top. Its clones are in the middle. The clones' clones are on the bottom.

Xena the cloned pig