Cloning comeback

The Sooam Biotech Research Foundation nestles on a wooded hillside in Guro, a district on the southwestern outskirts of Seoul. Spartan, quiet and cold on this winter day, the grey-white exterior belies the buzz of activity within.

A door just off the foyer leads to a corridor of canine chaos. In stalls to the left, Tibetan mastiff and Australian shepherd puppies are cavorting. A Yorkshire terrier dances back and forth on its hind legs. And an adult mongrel howls with separation anxiety, only calming down when the two beagle pups that she gave birth to are returned to her pen. She doesn't know that she is just a surrogate mother, nor that the pups are highly unusual dog clones, engineered to show the symptoms of Alzheimer's disease.

The right side of the corridor houses a wall-sized window that looks onto an operating theatre. Inside, Woo Suk Hwang, in a blue surgeon's gown, cap and mask, is working on a bitch in labour. He greets his visitors through a microphone headset and then explains that this is an emergency: one of...