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 Saturday, 28 December, 2002, 10:25 GMT
Cloning humans: Can it really be done?
Cloning graphic
Claims by a controversial company linked to a UFO sect that it has produced the world's first cloned human baby have been greeted with scepticism and calls for the process to be outlawed.

Our science editor, Dr David Whitehouse, answers some questions about cloning and whether the technology can be made to work in humans.

Q. How would it be done?

A. The model is Dolly the sheep and although the technology has been applied to several animals, it is still highly underdeveloped and the mechanisms involved are poorly understood.

The scientists would remove the DNA from the nucleus of an egg cell taken from the mother. This DNA would then be replaced by the genetic material taken from one of the father's cells (or as in this case, the mother herself) - perhaps a skin cell. A trigger would be applied to the egg cell that would then make it start to divide like any normal embryo. The mother would have it implanted in her womb in a procedure which is routinely performed in IVF clinics.

Q. So, what are the dangers?

A. Experience with the five mammal species that have been cloned so far indicates that there would be almost no chance of success.

The vast majority of pregnancies involving clones have gone very badly. In most of them, the clone has died and in almost all of them the lives of the mother and clone have been put at risk.

In many cases, the clone grows abnormally large, often threatening to tear the womb that can also become swollen with fluid. Almost all clone pregnancies spontaneously abort.

Dolly the sheep, the first mammal clone, was the one success in 247 pregnancies. If a human clone is produced, the cost in human suffering and the trail of failures will be large.

Q. What if a human clone is born?

A. Of the small number (little more than 1%) of animal clones that make it to term, most have severe abnormalities: malfunctioning livers, abnormal blood vessels and heart problems, underdeveloped lungs, diabetes, immune system deficiencies and possibly hidden genetic defects. Several cow clones had head deformities - none survived very long.

It would be fair to say that experts are amazed in the few instances that cloning has worked.

Q. Is it possible to choose healthy embryos for cloning?

A. Screening for suitable embryos will not work. Normal babies are made from the joining of genes from sperm and egg. Genes are "imprinted" - a poorly understood process that avoids any genetic confusion between similar maternal and paternal genes. There is evidence that in clones this imprinting does not work properly. There is no way to screen any embryo to detect this problem.

Q. What will happen if a clone grows up?

A. We know very little about the long-term health of clones. There is some evidence that they may not live as long as conventional humans and may have health problems. Studies are ongoing.

Q. Would the child be an exact copy of the genetic parent?

A. Not if the donor genetic material comes from a man or from another woman. On the genetic level, the clone would be 99.9% identical to its parent, but it would not be a complete copy because there are some important genes that would be contributed by the egg donor. These genes reside outside the nucleus.

Also, the clone would be subject to different environmental factors and a different upbringing to his/her genetic parent. This could result in a changed appearance and personality. If the recent research on the human genome has taught us anything, it is that we are far more than just our genes.

Q. But isn't all of this illegal anyway?

A. In most countries that carry out advanced biomedical research it is. In less developed countries, including some that offer test-tube baby programmes, there are no laws against it.

Just taking the UK as an example, there is now a specific law to ban the placing of any embryo in a woman's womb that is not created by a fertilisation process.

This was introduced a year ago.

All embryo research in Britain require a licence and you simply would not get one if you said you wanted to make human clones.

But remember, all of this is quite separate to therapeutic cloning. This is a more limited use of the Dolly technology to obtain important cells which could yield novel therapies for degenerative diseases.

Human reproductive cloning

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