The cloned food furore has been a timely reminder of how, even when we recognise a big idea, no one can quite predict its consequences. It is 13 years since the breakthrough that made it possible to clone adult animals was announced by a team at the Roslin Institute, University of Edinburgh.
Called nuclear transfer, it offered a way to wind back cellular time. The team used it to take the mammary cell of a sheep and turn it into an embryo, which then grew into a clone of the sheep. The clone was called Dolly.
Headlines reflected the shockwaves her birth sent out: they raised ''dreaded possibilities'' such as ''the abolition of man''.
One writer described how Dolly ''looks at you with those intense red eyes - eyes full of hate''.
But rather than a red-eyed menace, the Edinburgh-based Dolly is an affable, plump sheep. And the scientist who led the cloning effort, Sir Ian Wilmut, is no Dr Frankenstein, but an ordinary bloke with a beard.
Little has changed since then. Even though there are plenty of clones around us - identical twins, bananas, potatoes, bacteria - the word still triggers knee-jerk fear.
The current palaver concerns the use of nuclear transfer to copy endangered species and elite breeds, along with pets. Copies have been made of wildcats, wild ox, a mouflon (an endangered species of sheep), racing horses, mules and camels.
American companies clone cattle, horses and pigs for breeding on farms. It was never likely that consumers would find themselves eating pork chops made from cloned pigs, because the process is so inefficient and expensive. Instead the goal has been to clone prize animals and breed from them.
As Wilmut says in New Scientist, before Dolly, thousands of embryos had to be injected with foreign DNA to get a handful of GM animals. But he realised that you could use cloning to make a whole animal from a single genetically modified cell.
The first demonstration of this idea - the original driving force of Wilmut's work - came with the birth of another sheep, Polly, who could make a human blood-clotting protein (the scientific joke being that she was a ''pharm animal''). Today there are goats that make an anti-coagulant protein in their milk, cattle which make disease-fighting antibodies and ''humanised'' animals that can produce organs for research or for donation. But such commercial applications have appeared more slowly than Wilmut hoped, and rival methods are ever more efficient.
Then there is the case of ''therapeutic cloning'', where nuclear transfer would be used to create cloned embryos of patients. These are allowed to develop for only a few days before being dismantled for their stem cells, used to repair disease and damage. This method, too, began to be eclipsed in 2006 when Shinya Yamanaka, of Kyoto University, made human embryonic stem cells directly from adult cells, avoiding the ethical debates over the use of cloned embryos and human eggs, which are in short supply. Wilmut used this technique to create the two main cell types involved in motor neurone disease.
The final possibility is the most frightening: ''reproductive cloning'' to create humans. While there are ethical and psychological objections, the main problem is safety. Cloning is linked to a higher death rate for foetuses and problems during birth.
To repeat the Dolly experience in humans would mean obtaining 300 eggs and persuading 29 women to have a cloned embryo implanted. Of those, the odds are 28 would fail, with only one embryo ''taking''.
Wilmut concludes that to clone humans would be ''utterly irresponsible''. For now, the most pressing issue raised by Dolly's legacy seems to concern what we eat and drink.
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