快猫短视频

EVE was born by Caesarean section on 26 December at an undisclosed location. Her 鈥減arents鈥� are American and belong to the Raelian cult. And that is all we know with any certainty.

According to Clonaid, a company set up by the Raelians, Eve is the world鈥檚 first human clone, created from a skin cell taken from her 鈥渕other鈥�. More astonishingly, Clonaid claims she is not the only one. On 3 January, it says, a second clone was born, to a Dutch lesbian couple. And, Clonaid claims, three more are due to be born soon.

At the press conference in Florida to announce the birth of Eve, Brigitte Boisselier, who heads Clonaid, said that Michael Guillen 鈥� a trained physicist and former science editor for the USTV channel ABC 鈥� would oversee independent tests to confirm that Eve and the other babies really are clones.

But so far there is no sign of this happening. Eve鈥檚 鈥減arents鈥� have apparently been having second thoughts about testing. A case about to be heard in Florida, calling for Eve to be placed under court protection, is not likely to help persuade them.

Guillen has now suspended the testing process, saying his team of scientists has not been given access and admitting that it could all be 鈥渁n elaborate hoax鈥� to get publicity for the Raelians. His own reputation has also come under fire, especially after it emerged that he tried to sell exclusive rights to the cloning story last year.

An answer may be some time in coming. But whatever the truth, Clonaid is not alone. The controversial Italian fertility doctor Severino Antinori has claimed that a cloned baby will be born in January. His erstwhile colleague Panayiotis Zavos last month announced plans to clone babies for seven infertile couples. And there may be other would-be cloners out there who are keeping their plans to themselves.

How difficult is cloning?

So is it really feasible that renegade scientists could clone a human?

The answer has to be yes. Unlike making nuclear weapons, cloning requires no large-scale infrastructure. What is needed is a small team of scientists willing to try it despite the serious risks to both the child and the mother; a million dollars or more; and, above all, lots of human eggs. This last requirement could give an offbeat religious sect with plenty of eager volunteers a big advantage.

Last year Boisselier claimed Clonaid had collected over 300 human eggs for its experiments and had lined up 50 women to carry cloned embryos. If true, such numbers would give practised cloners a good chance of success. Some animal cloners achieve up to three live births for every hundred eggs.

The techniques are not overly difficult to master. Although methods vary from lab to lab and species to species, cloning usually involves removing the genetic material from an unfertilised egg and replacing it with that of an adult cell. 快猫短视频s then fool the egg into thinking it has been fertilised, usually with an electric pulse.

The key tool is a micromanipulator, found in most IVF labs. This allows a skilled technician to grab an egg cell under a microscope, suck out its nucleus with a fine needle and then inject an adult nucleus using another needle. An alternative is to fuse the empty egg with a whole adult cell.

Eggs are easily damaged, and manipulating them is tricky work requiring patience and a delicate touch. Even so, a few months of practice on cows鈥� eggs taken from ovaries bought from a slaughterhouse is usually all it takes to get the hang of it, says Jose Cibelli of Michigan State University.

Cibelli and his former colleagues at the Massachusetts-based cloning company Advanced Cell Technology are the only scientists to date to have attempted to clone human embryos and publish the findings. Their aim was to obtain human stem cells. The results were not good: in 19 attempts only three embryos started dividing, and the growth stopped soon.

But Cibelli puts this down to a lack of human eggs. 鈥淪uccess in cloning is a numbers game,鈥� he says. 鈥淲ith cows we have hundreds of eggs. In humans, that鈥檚 a luxury you don鈥檛 have.鈥� ACT had to pay its egg donors $4000 each.

Last year, Chinese scientists claimed to have done much better, getting dozens of cloned embryos to grow well past the stage at which they are normally implanted during IVF. But these claims have yet to be confirmed.

What鈥檚 more, not every mammal cloning programme has succeeded. The millions of dollars spent on dog cloning have so far failed to produce a single cloned puppy, and extensive efforts to clone rhesus monkeys have not led to a single successful pregnancy. However, many experts believe that these efforts have failed because these species鈥� reproductive systems are unusually difficult to manipulate, rather than because of any fundamental barrier.

For instance, when scientists created ANDi, the first genetically modified monkey, their main difficulty was keeping the monkey embryos alive in culture beyond the four-cell stage. During IVF, human embryos are routinely grown past this stage.

All this suggests that, in theory at least, maverick scientists could indeed clone a baby. But has Clonaid really done it? According to Cibelli, the main reason to be suspicious is that it claims to have produced not just one cloned baby, but two, with another three on the way and just five miscarriages. To have five clones born live from just 10 attempts would represent an astonishing success rate 鈥� especially since in Cibelli鈥檚 experience human eggs are more fragile than cows鈥� eggs.

He is also surprised that Clonaid claims to have achieved all this by cloning skin cells. In his experience, the cumulus cells that surround developing eggs are better donors.

Yet animal work has shown that cloning is something of an art. Success can be unpredictable and inexplicable.

Is cloning safe?

If little Eve really is a clone, she could suffer a host of serious health problems. Some might not show up until she is in her sixties 鈥� if she survives that long.

Although scientists still do not understand exactly why, cloning is very risky for both the offspring and the mother. In every species that has been cloned, the vast majority of cloned embryos die before birth. And even the clones that survive to birth often have debilitating or fatal problems.

鈥淭here is absolutely no reason to expect the situation to be different in humans,鈥� states a letter put out by cloning experts Randall Prather and Gerald Schatten, and the creator of Dolly the sheep, Ian Wilmut. 鈥淯ntil there is compelling evidence that the situation is different in human embryos, it is grossly irresponsible to attempt to clone children.鈥�

Cloning involves transferring the genetic material of an adult cell such as a skin cell 鈥� reportedly used to create Eve 鈥� to an empty egg. But a skin cell is 鈥減rogrammed鈥� to be skin. That is, the genes needed for skin are turned on and the rest are turned off. For a cloned embryo to develop normally, the skin genes need to be turned off and embryonic genes turned on.

Putting an adult nucleus into an egg does somehow reprogram it, but this process is far from perfect. And the physical transfer of the nucleus can also damage the delicate egg. The result is that some embryos never divide, while others don鈥檛 grow enough to be implanted into the uterus of a surrogate mother. Those that appear healthy enough to implant often spontaneously abort or are stillborn. Only a few per cent survive to birth.

The fetus isn鈥檛 the only one at risk. Cloned animals and their placentas can be unusually large. That poses a serious threat to the life of the surrogate mother. A 1999 study of 12 cows pregnant with cloned embryos found that a third died from complications.

The few cloned animals born alive often suffer from a surprisingly wide array of deformities. These include: lung and heart problems; huge tongues; flattened faces; bad kidneys; blocked intestines; weak immune systems; twisted feet and gross obesity a few weeks after birth. The defects are sometimes so severe the animals have to be put down. In humans, they would require lifelong treatment.

Cloning companies claim most cow clones that do survive are perfectly healthy. They point out that 鈥渓arge offspring syndrome鈥� also occurs in cattle created by IVF, so the problem may be poor culture conditions rather than cloning itself. And pig cloners report far fewer birth defects, suggesting some species are easier to clone than others.

However, other scientists say it is too early to declare any clone normal. It is just six years since the birth of Dolly, the first cloned mammal, and few clones other than mice have yet lived out their natural lifespan. Dolly herself prematurely developed arthritis.

What little we know suggests clones might die earlier than normal. A year ago, Japanese researchers reported that 83 per cent of their cloned mice died after two years 鈥� over three times the rate for mice created by IVF or normal breeding. And some tests on cows suggest that clones are even less bright than the average bovine.

Would-be human cloners have always pledged to screen out defective embryos to eliminate problems encountered with animal clones. Boisselier told 快猫短视频 that Clonaid had looked at gene expression in the cloned human embryos it created and found no problems, but she would not reveal any details.

Most experts say comprehensive tests of this kind can鈥檛 be done, because the genetic defects in clones are believed to be too subtle and too widespread to screen for with existing technology. Researchers recently showed that there are dramatic abnormalities in the level of activity of hundreds of genes in the placentas of cloned mice. They also detected a similar but lower level of genetic chaos in the livers of newborn mice clones. Measuring and predicting the effects of these abnormalities in every tissue of a developing fetus is impossible.

How can we tell if a clone really is a clone?

Verifying whether a baby is a clone or not is straightforward with modern DNA fingerprinting technology. But with all the secrecy surrounding maverick cloners, satisfying sceptical scientists will not be easy.

鈥淓xtraordinary claims have to be supported by extraordinary evidence,鈥� says the inventor of DNA fingerprinting, Alec Jeffreys of the University of Leicester. 鈥淭hat means bringing into force the full weight of forensic DNA typing systems, including all the safeguards and procedures that exist in that technology.鈥�

DNA fingerprinting looks at highly variable regions of our genome, in which short sequences are repeated many times. The number of times a particular sequence is repeated varies from person to person, and on each of the two copies of each chromosome. The chances of two people having the same pattern is extremely small.

A normal child鈥檚 DNA fingerprint would be a combination of those of its parents. But a cloned baby would have just one 鈥減arent鈥�, and their DNA fingerprints should be exactly the same. Of course, mutations can occur in any cell in the body, so it is possible that the clone鈥檚 profile would differ very slightly from the 鈥減arent鈥�, requiring further testing.

However, it is not enough for self-proclaimed cloners to provide matching samples. They have to prove that one sample is from the child and the other from the person cloned. Given the controversy surrounding such claims, it is crucial that the entire process is foolproof. 鈥淲hat you need is some trustworthy person to take the samples,鈥� says Rudolf Jaenisch, a cloning expert at the Whitehead Institute in Boston.

Jeffreys goes further. He insists that the sampling and testing should be done independently by not just one, but two labs. 鈥淚deally, the entire procedure should be videotaped all the way through to ensure that there鈥檚 no possibility of sample substitution.鈥�

Even then, Jeffreys suspects that more testing will be called for. 鈥淭he scepticism in the scientific community will be so intense that there will be some suspicion that very clever substitution has occurred,鈥� he says.

But there is a way to check. A little of the DNA in cells is found outside the nucleus, in organelles called mitochondria. The mitochondria in a clone come from the donor of the egg, rather than from the person cloned. So as long as Eve鈥檚 mother didn鈥檛 provide the donor egg as well as the skin cell that was cloned, a mitochondrial DNA test could help settle any argument over the source of the samples.

Can we stop would-be cloners?

鈥淲e must prevent human cloning by stopping it before it starts,鈥� announced President Bush last April. Yet if Clonaid is to be believed, the first human clone was already growing in her mother鈥檚 womb as these words were uttered.

Despite the almost universal condemnation of the renegade cloners such as Clonaid, preventing human cloning will not be easy. Since Dolly the cloned sheep was born six years ago, the prospect of human cloning has prompted over 40 countries to ban it (see Map). There has also been an attempt by the UN to piece together an international treaty banning human cloning.

But even if such a treaty gets off the ground, it will only be effective in the states that sign up to it, says Frederick Kirgis, an expert in international law at the Washington and Lee University in Virginia. Each country would have to amend its domestic law to bring the treaty鈥檚 provisions into force, which could take many years. And there is always the possibility that non-signatory states will allow human cloning to go ahead.

UN treaties can often be breached with impunity, says Kirgis. 鈥淪ome treaties have enforcement mechanisms written into them,鈥� he says. 鈥淏ut most of them don鈥檛.鈥�

Despite broad support for a ban, not to mention the new sense of urgency brought on by the announcement of Eve, there is still a complete lack of consensus on how it should be carried out, says Arthur Caplan, a bioethicist at the University of Pennsylvania in Philadelphia and an adviser to the UN committee dealing with cloning. The best we could hope for at present is a moratorium, he says.

The problem is that while some countries want a blanket ban on all forms of human cloning, others such as Britain believe any ban should exclude therapeutic cloning 鈥� creating cloned embryos to obtain embryonic stem cells for treating diseases.

To get round this, some countries have suggested that the UN should ban reproductive cloning now and worry about therapeutic cloning later. But Spain and other states oppose this because they see no legal or moral distinction between therapeutic and reproductive cloning.

Nowhere is the division on this issue greater than in the US. George Bush has lent his support to a bill that would make human cloners liable to up to 10 years in prison and a $100,000 fine. A second bill introduced by Republican senator Arlene Spector would ban only reproductive cloning.

Perhaps the way forward would be to copy South Korea鈥檚 approach, where last week officials raided Clonaid鈥檚 local subsidiary. Korean law does not ban cloning, but officials are considering bringing charges on the grounds of unsafe medical practice.