'Disease models' set to play crucial medical role

In 1996, Dolly the Sheep became the world's first large cloned mammal. However, she was a latecomer, as tadpoles were cloned back in 1952 and mice in 1986.

Dolly was followed by Snuppy, the world's first canine clone, born in South Korea in 2005. To date, more than 20 types of mammal have been cloned successfully, including cats, dogs, mice, horses, sheep, pigs and cows.

Last year, scientists at the Chinese Academy of Sciences cloned monkeys using the same technique that produced Dolly, marking the first time that primates had been cloned successfully.