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Wednesday, 16 August, 2000, 11:11 GMT 12:11 UK
'Cloning' to beat genetic diseases
Diagram of human egg
Experts have given their approval for cloning techniques to be used to prevent often lethal genetic diseases carried by the mother.

A variety of rare but devastating defects are caused by problems with genetic information contained in the mother's egg, but outside the nucleus, in which most of the genes are kept.


Perhaps future generations now may have a chance

Paul Preston, Children's Mitochondrial Disease Support Network
The disorders that follow can affect many different parts of the body, including the central nervous system and brain, and many prove fatal to the child at a very young age. Most leave the child disabled, some terribly so.

The treatment proposed would involve taking the complete nucleus from the affected woman and placing it inside a human egg from which the nucleus had been extracted.

embryo
The embryo would be produced using eggs from two women
This resulting egg would then be fertilised using normal IVF techniques and any resulting embryo reimplanted into the woman.

So the embryo would develop using the nucleus from the woman carrying the mitochondrial disorder, but with the mitochondria from an unaffected woman, hopefully then removing any chance of the child being born with a defect.

While the technique uses cloning technology, it is not actually cloning in the true sense of using a single cell from an adult to create an embryo.

The altered egg would still be combined with the genetic material of a male during the fertilisation process.

There are procedures available that can screen women for mitochondrial defects which they might pass on - but because of the rarity of the condition, these are generally only offered after the birth of an affected child.

Devastating effects

The announcement, among a raft of others approving limited human cloning for therapeutic reasons, has delighted support groups.

Paul Preston, Chairman of the Children's Mitochondrial Disease Support Network, strongly welcomed the announcement.

Of his three children, one has already died from the condition, and two have been left severely disabled and dependent.

He said: "Perhaps future generations now may have a chance. This is an absolutely necessary step and it has been a long time coming."

The impact on his own family had been enormous, he said.

"We rarely get more than a few hours sleep a night because we have to get up to look after the children.

"We can't do any of the things a normal family does like go on holiday, or go out - it's simply too difficult."

Mitochondrial disorders are thought to affect as many as one in 10,000 children in the UK.

Problems in the mitochondria stops the body's cells processing energy, leaving them unable to perform their functions properly.

When this happens in the central nervous system, the result is very severe disability.

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Professor Liam Donaldson, Chief Medical Officer
"We know already the number of laboratories that will be able to undertake these techniques"
See also:

16 Aug 00 | Sci/Tech
Experts support human cloning
31 Jul 00 | Sci/Tech
Q&A: Therapeutic human cloning
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