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Last Updated: Wednesday November 05 2008 13:40 GMT

Scientists clone frozen mice

A brown mouse scientists cloned from brain tissue taken from a frozen mouse

Japanese scientists have successfully cloned mice from dead mice that have been frozen for 16 years!

Cloning isn't new - in the past, sheep, horses and even a pet dog have all been cloned from living animals.

But now scientists have found a way to clone dead animals, as long as their remains have been frozen to preserve their unique genes.

They're also hoping they can one day use similar techniques to clone species that died out years ago, like mammoths.

The frozen mice scientists used to clone another mouse
One of the frozen mice
So how have the scientists done it?

When the mice died, they were frozen in a special science lab freezer.

Years later, scientists removed brain cells from the frozen mice to take samples of their DNA - a unique pattern of cells that determines how every living creature develops.

Then they injected the DNA into an egg, which was implanted into a healthy living female mouse. Weeks later, lots of the cloned baby mice were born.

But not everyone thinks it's a good idea. Some people are worried that cloning animals isn't safe and could cause more harm than good.