Quick Guide: Cloning
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Introduction

Embryo cloning

Reproductive cloning

Therapeutic cloning

Benefits

Concerns

Reproductive cloning
Dolly was the first mammal cloned using adult DNA cells

Reproductive cloning is contentious as it seeks to create a living duplicate of an existing animal.

DNA is removed from an egg and replaced with DNA taken from an adult animal, making a genetic twin.

Then the fertilised egg, now called a pre-embryo, is implanted in a womb and allowed to develop into a new animal.

Until the birth of Dolly the sheep in 1996, there was doubt this would work in mammals, but now some scientists say they are trying to clone a human.