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The plan has provoked an outrage on moral grounds, but experts in the
field doubt whether the men can actually deliver on their promises.
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 - 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. But is it really feasible?
A. Zavos and Antinori could well have the equipment to attempt human
cloning. They say they have the volunteers. Certainly, the techniques
required are all recorded in precise detail in scientific journals. But I
stress again, the technology is poorly understood and fraught with dangers
for both the mother and the child.
Q. So, what are the dangers?
A. Experience with the five mammal species that have been cloned so far
indicates that Zavos and Antinori have 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. Zavos and Antinori claim to be able to "quality control" embryos
choosing only "healthy" ones?
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. No. On the genetic level, the clone would be 99.9% identical to its
parent. 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 no law that specifically
prevents human cloning. However, all embryo research does require a
license and you simply would not get one if you said you wanted to make
human clones. And if this seems like a loophole, it will be closed very
shortly. The government says it will bring forward legislation that
specifically bans the copying of humans for reproductive purposes.
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.