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Wednesday, 15 August, 2001, 12:14 GMT 13:14 UK
Cloning humans 'easier' than animals
Lab researcher
Cloning humans might be easier than first thought
A group of scientists carrying out research into human genetics say cloning humans may actually be easier than cloning animals.

Their conclusions have been criticised by experts in Britain.

The news follows a recent announcement from an Italian fertility doctor that he intends to begin cloning humans to help infertile couples have children.

Many scientists reacted with horror when Dr Severino Antinori announced his intention to clone humans.

Those involved in animal cloning warned of huge practical problems - many clones die early or are born with genetic deformities, and develop diseases such as cancer.

Genetic difference

In this latest research, scientists at Duke University Medical Center in North Carolina say the cause of all these problems may be one specific gene, which is responsible for controlling the way in which cells grow.

Mammalian cells in lab
Fewer than one in 300 cloned sheep embryos develop normally
When it is not working properly, cells can grow in an uncontrolled way. This can cause cancer tumours to develop.

In normal sexual reproduction a copy of this gene is passed from each parent to the offspring. But in many animals other than humans, one of these genes is turned off.

The cloning process affects the remaining active gene; it cannot work properly, and so the cloned embryo grows in an uncontrolled way.

Ageing Dolly

For example, in sheep less than one embryo in 300 develops normally. Even the world's most famous sheep clone, Dolly, is suffering from problems linked to this gene - she is rapidly ageing and overweight.

Dr Randy Jirtle of Duke University told the BBC that he and his colleagues found this genetic difference while looking at the evolution of genes. They say this difference arose about 70 million years ago to help control the size of babies in the wombs of very early human ancestors.

The researchers also say finding that the gene works in a different way in humans from animals such as rats and mice has raised questions about large areas of medical research.

They say many drugs rejected because they cause cancer in these animals could be looked at again.

'Dangerous' information

The findings are published in the journal Human Molecular Genetics, but have been criticised in Britain.

"It seems that a little knowledge is a dangerous thing, and the authors have allowed themselves to over-interpretate their interesting results," said Professor Ian Wilmut of the Roslin Institute, in Edinburgh, leader of the team which cloned Dolly the sheep.

"I hope that this will not be used to give encouragement to those who wish to clone humans," he said.

Dr John Parrington, a cloning expert at University College London, pointed out that more than one gene behaved in a way that might cause problems in a growing cloned human embryo.

"You can't say, taking this information in isolation, that it's easier to clone primates and humans," he said.

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