The most advanced human embryo clones yet have been produced in order to obtain cells to learn how to treat diseases such as Alzheimer's.
South Korean scientists took genetic material from normal cells in women donors and combined it with their eggs.
The 30 resulting embryos were grown up to produce stem cells that can divide into any tissue in the body.
It is hoped that the cells can be used to replace ones that have failed in patients with degenerative diseases, such as Parkinson's.
The team sought approval for its work from an ethical review board before proceeding with the work.
Does this work signify a breakthrough in the treatment of some diseases? Or is the ethics of therapeutic cloning still in question?
This debate is now closed. Read your comments below.
This debate is now closed. The following comments reflect the balance of views we received:
First, congratulations. Therapeutic cloning will have a bigger impact on human health than the development of antibiotics. The benefits of this new field of treatment must not be thrown away because some people cannot see the difference between this and the abhorrent risks to potential offspring of reproductive cloning, which should of course see an immediate, complete worldwide ban.
The nature of life is evolution now we are preparing the technology to stop that evolution by creating copies of our selves. I believe that this type of technology will be something like the technology that created the nuclear bomb. It just one of those things that we would like to un-invent but that will not be possible.
Bill M, Greece
Think about the potential of this breakthrough in saving lives and reducing human suffering as long as it is carefully handled.
Hsiang, Hong Kong
The problem with this issue is that the Social Sciences are not keeping up with the physical sciences. If we choose not to allow natural selection to keep our gene pool clean, we will then have to find other ways to do so, and cloning is one of them.
Garth, Harare, Zimbabwe
It's a great day for science.
Joseph Fowler, London, UK
If a human plays with nature then nature is bound to reply back. It's only a matter of time when nature shows adverse reaction to create its balance again. Science should not interfere with nature otherwise humanity would suffer unpredictable consequences.
Sheraz Ahsan, Quetta, Pakistan
I can see the benefits but to be honest this could be more catastrophic than splitting the atom. There are something you shouldn't mess with!
Peter Crosby, UK
It is a significant breakthrough in science. If the uses of cells from the embryo clones are limited to treating diseases, the benefit to the world will be tremendous.
Jaward Sesay, Philadelphia, USA
If through this method we maybe save lives, why not try?
Ying Ying, Singapore
Why do people like to meddle with nature's way? It hurts us if one of our relatives or loved ones get sick but let's leave nature to take its course. Don't you think? What is meant to be is meant to be, no one can change God's will, it's like we are cheating death or sickness.
Alia, Beirut, Lebanon
This is a great day for science! I hope this will improve our lives. Government should put more money into this.
Miikka Koskinen, Helsinki, Finland
A group of cells has no thought or feeling. It is not aware. Thoughts and feelings are what makes us human not our cells. Stem cell research should continue and cloning technology should be watched like a hawk for misuse.
Robert Pinder, UK
Individuals in the general community should have at least a basic understanding of human genetics before they raise their thoughts and opinions about the risks and implications of human cloning. True, everybody has a right to an opinion; but opinions based on superficial knowledge and obscure sources of information are not only useless, but damaging.
How is this any different that when multiple embryos are fertilized for IVF and then "selective reduction" is performed. People don't think twice about the fact that lives were created and destroyed in that process as well. If stem cell research can help cure some of our most prevalent diseases such as cancer, research will have to go forward.
Jill, Philadelphia, PA USA
The benefits of stem cell research far outweigh the downfalls. By destroying embryos, we are furthering research that will add tens of years to the lives of people experiencing certain diseases, such as Parkinson's disease. An ethical question: should we be sacrificing day-old embryos to save people who are already alive?? Yes.
Anna Taelor, London, UK
There are many sources of stem cells. Most involve no loss of human life at all. Harvesting human embryos is the glaring exception. Using stem cells gained from umbilical cords or placentas can contribute to scientific research into diseases such as Parkinson's without any loss of life. Why do some people object to such ethical medical research? Given the alternative sources of stem cells available today, you have to question the real agenda of those promoting human embryo farming.
Mike, London, England
The benefits have yet to be gained but clearly if we allow the naysayers to halt research we are standing in the way of the most potent advance in medicine for centuries. There will always be moral and philosophical differences of opinion on the embryo issue. But to those of us who have seen lives cut woefully short by cancers and Alzheimer's, to have the potential to reverse these horrible and tragic diseases is a very powerful argument.
The concept of farming human life for medical purposes is revolting and preposterous - akin to cannibalism. A frighteningly cavalier attitude is being taken towards human life. Fundamentally inhuman, it is being justified in the name of helping humanity. Humanity will suffer increasing degradation, until we realise that life is sacred, a gift from God and not the plaything of human beings.
I'm sorry to say that research shows so far that embryonic stem cell research may well be a scientific dead-end. Like "squaring the circle", it is unlikely ever to produce positive results. Why is this? Simply because the cells themselves are too volatile. Whilst all the media attention is focused on ESCR, huge advances are taking place with adult and umbilical cells.
John Airey, Peterborough, UK
It's a fact. There is nothing to be gained from questioning the ethics of the decision as it's already history. Reproductive cloning will no doubt follow in due course. Lets debate the ethical issues and how best to reconcile these developments with society but lets all refrain from coming over all superstitious.
Dave, Leicester, UK
I wonder where we are heading with this type of research. The lifespan built into our genes is an important part of nature's checks & balances. I can foresee that in a few years time, nobody is going to die of anything except for accidents and warfare. Does this really benefit mankind? The planet is already suffering from a lack of essential resources due to over-population. We tamper with these fundamentals at our peril I fear.
Chris, Brazil (UK)
In recent years, adult stem cell research has been achieving far greater success in curing debilitating diseases than human embryo cell techniques. None of this is reported, however. I wonder why. For example, 4 years ago, French researchers reported the first clear success in human gene therapy, curing severe combined immunodeficiency disease (SCID) in several children by inserting the missing gene into their bone marrow stem cells (i.e. without an embryo stem cell in sight). Those who still excuse the use then destruction of human embryos have a lot of explaining to do. This latest development in S. Korea is unnecessary and unethical. I urge everyone to read the science and ignore the adherents of a brave new world.
Mike, London, England
People who don't see the point of all this kind of research are not aware of the benefits all these scientific progressions are bringing to us.
Eduardo de Souza, A Coruna, Spain
If you want to go against this form of curing people, you must be against abortion, euthanasia, and, effectively, contraception. All of those things destroy a potential human life, but none of them help an existing life, with both quality and longevity.
Derry, Slough, UK
I wonder, will those who condemn this research turn down treatment if they themselves get sick?
Ruth, New York, USA
All I can say is that I am glad the hypocrites who oppose scientific advancement will be ignored, and hopefully will be laughed at by future generations.
Richard Murray, London, UK
A cell is not a human. You kill millions of cells a day just during everyday life. Cloning cells for medical research has about as much to do with creating humans, as making a brick would have to do with New York City.
People complain about "playing god"- what about them? Does imposing baseless moral objections, and potentially depriving millions of people of life-saving medical technology sound reasonable to you? Their arrogance and heartlessness makes me sick.
Richard Murray, London, UK
To create human life with the intention of sacrificing and destroying it later is inherently evil whatever the motive.
I fully applaud this breakthrough. However many scientific hurdles must be overcome before the utility of this approach can be fully realised.
Ray Chan, Edinburgh
Playing God? We've always poked our nose into God's secrets. We are a naturally curious species. We ALWAYS open Pandora's Box, we can't resist it. When US scientists detonated the first nuclear bomb they believed there was a small chance the whole world would explode in a chain reaction. They still did it. And we will play with our DNA, it's just too tempting and exciting.
Science fan, UK
Before we discard the pro-life arguments as anachronistic I'd like to remind everyone that "We were all embryos once" !
Dave Houlton, Weil am Rhein, Germany
It's the only way forward.
Jamie Samat, Northants, UK
Has long as they don't try to clone Blair and Bush, I say go for it.
Scott Peck, Tucson, USA
An embryo is not a living, feeling, walking, talking human being. Its just a few cells that can become a human being. If we can use this research to cure a live, breathing, suffering human being by using these cells, then us as humans should be all for it. I say make this research top priority over all the other junk going on in the world.
Ken, New York, USA
A remarkable scientific achievement. A sad day and regrettable milestone for humanity.
Ricardo Rodrigues, London, UK
Its when science is used in a positive way to the benefit of mankind then it can only be a good thing.
Lyndon Patrick Berchy, Edam, The Netherlands
I applaud their breakthrough, but fear the implications.
Chris, Deltona, FL, USA (UK ex-pat)
The ethics of all this boils down to what we consider a human to be. My belief is that what makes us human is our brains, our great capacity for thought. A five day embryo does not have a central nervous system; therefore it is not yet human. And, more importantly, it can't feel a thing.
The danger lies in who will clone and for what reasons. Not everyone with access to this knowledge and technology will be concerned with saving lives or ending suffering. As with every other advancement in our knowledge this can and will be exploited for all the wrong reasons. This time let's learn from previous mistakes and be vigilant and very, very cautious.
Roger, Wrexham UK
This is a promising technique for treatment of Alzheimer's and Parkinson's - but it should never be used for reproductive purposes.
Andrew Walden, Hilo, Hawaii, USA
Being able to create a stem cell with the DNA of the intended recipient may significantly reduce the chances of rejection by the body. This has the potential to be a huge breakthrough for medical science.
John Westfall, Los Angeles, USA
Fantastic! My father died last year after having Parkinson's. This was a cruel illness that robbed him of the ability to walk, talk, and eat properly. We are all here due to the advancement of science. I say three cheers for these men and don't let the luddites get away from progress.
Nigel Machin, Staffordshire
It seems very clear that there are two clear groups - people who embrace the potential that therapeutic cloning has to offer, and those who confuse a 5 day old embryo with a fully grown sentient human being. Scientists are not doing this to make a name for themselves - it's to try and cure diseases.
Alison, Leeds, UK
Here's some food for thought. What if it was YOU who was aborted as a 5 day old embryo, never given the chance to experience life? Would you still support the science?
There is no such thing as therapeutic cloning; it's just cloning. Stem cells can be harvested from adults with no loss of life. Whatever 'ethical committees' say, no rational person has to fool themselves. This is science taking a wrong turn.
Dudley Plunkett, Southampton, UK
The future of human cloning will be determined, like everything else, upon its chances of making a few guys filthy rich.
Topaz, Tampa, Florida USA
This new research can only be heralded as a scientific breakthrough. One appreciates that there will be murmurs of discontent from people who perceive the treatment to be unethical. However, if one takes into account the help it brings to Alzheimer disease sufferers, then only one can see the benefits it will have on those that suffer from this tragic illness.
This is a topic that clearly raises passions in people that are both for and against it. Personally I feel that the science should be allowed to continue. If stem cells could save someone I love then I would want them to benefit from it. I am not sure however if I myself would allow someone to treat me with stem cells taken from a human embryo, I think the guilt might get to me.
The assumption by those that are pro-cloning is that anyone against it is ill-informed. That is not the case. My views are simple, the end does not justify the means. Abortion was just the first step toward devaluing human life. As a pregnant woman, I cannot believe that people do not care about using humans as scientific experimental fodder. I shudder to think what kind of world my baby will have to live in.
Aimee, Michigan, USA
When a human egg is fertilised a new human being is formed. Allowing scientists to set an arbitrary date when this person is protected from grisly experiments or abortion is so abhorrent to any civilised person. It really turns my stomach to think of it. My son was born with an under-developed left thumbnail - the paediatrician said he had obviously been sucking his thumb from about 11-12 weeks in the womb. Can a lump of inhuman tissue seek the solace of sucking it's thumb? I think not.
Catherine Davies, Bristol, England
This announcement, and others like it, have caught the West in a moral no-mans land. We never debated issues such as abortion, morning after pills and the like. What chance do a generally selfish and morally bankrupt community stand with an issue of this magnitude when we can't even debate the comparatively simple issue of abortion without fists flying?
Matt, Amsterdam, Netherlands (ex. UK)
The real crime here is that most of the interest is in raising research funds and nothing to do with saving lives. People's hopes are being raised; at the best, any practical use is decades away. All this technology is strong on promise and short on success. Don't anyone count their chickens yet.
V Breeze, UK
It may have its myriad benefits and ethical complexities, but isn't it perhaps opening a Pandora's Box? Once therapeutic cloning is as common as much, what's to stop the next big push - cloned children then genetically engineering clones? I fear that it may begin a walk down a path not so easily retreated.
Christopher Hogarty, Oxford, UK
I believe in the scientific and medical advances that will follow this research without fail. However, to clone an entire human who will be integrated into our society is something I fail to understand. The importance of stem cell research is obvious to me, but it seems that to clone an entire human, short of needing the brain, would be pointless on a scientific bases. Than again, I'm young. I do wonder though if cloning one gender over the other is any easier?
This research must continue for good of everybody in the future. In my opinion there is no valid argument or reason as to why this research should not take place. As for those who quote morals and ethics as reasons to stop the research, I would counter that it is immoral and unethical not to explore cloning, as ultimately we will gain a better quality of life from this work - not just for us but for every living thing on this planet
If this can help people had longer and healthier lives then I'm all for it.
Lou, West Midlands
If you don't live up a tree and eat grubs and berries then you are a down right hypocrite - you criticise scientists, when you owe everything you have and quite probably your very existence to them - how many of you would have made it to this age had we still been treating measles with "eye of newt"?
Lee, Stevenage, England
I can't believe some people actually question whether or not animals are equal to human beings! One human life from conception to death is more important that all the animals that ever existed! With this said however, animals are fantastic creatures. Any non-medical research carried out on them is totally barbaric but medical research is tolerable providing the animal is exposed to as little pain as possible.
Luke O'Sullivan, Swansea, Wales
Reading all the opinions of people on this page, I am struck by how many of them have misguided views about the science involved. Nothing science is attempting with cloning human cells has not been done before. Cells are being created. Not human beings. Cells. We have engineered both normal and cancer cells of both humans and animals to express the characteristics we want for decades. Why is this different?
Constantine Markides, PhD, Houston, Texas
I suppose we shouldn't use contraception either? That is the same sort of idiotic rubbish which has left a third of Africa with aids. Of course there needs to be some regulation, but anyone who preaches that using an unfertilised embryo is like killing a child is ill informed and plain wrong.
Paul, Wales: There's no such thing as an "unfertilised embryo". What was that you were saying about people being "ill-informed"? 100 years ago trainee doctors were taught that human life begins at conception. 50 years ago they were taught the same thing. Now they are taught that we don't know when life begins. This loss of medical knowledge over time is purely for convenience.
Andy, Annandale, USA
This is absolutely fantastic medical advancement. My father-in-law died of Alzheimer's it was terrible to see. Anything to find a cure.
Jennifer Owen, Gloucester
The human being is an end in itself and not a mean. We cannot "use" the human being as a "lab rat". If a person accepts to be tested or to undergo experiences, he has chosen deliberately to take part in the experience. Does an embryo choose to be tested?
With research on using stem cells from other sources gaining momentum it seems inappropriate to pursue this line of development with its accompanying ethical problems. If the technology to clone humans is developed, how do we know it will not be abused?
For the last seven years I have nursed my wife who suffered from motor neurone disease. She died three weeks ago, when all she could do was move one finger. She was on a ventilator and tube fed. She was 57.
She always believed stem cells would save her but it was not to be. However, if this could be the way for a cure, I say go ahead. I would not like anyone else to suffer as my wife and myself suffered with such a terrible disease...
Robin Milham, Elm Nr Wisbech UK
A human embryo cannot feel pain so what is the big fuss about? The majority of human embryos get spontaneously aborted in nature due to genetic abnormalities. So to claim that every embryo is sacrosanct, a fully functioning human being like you and me but for the passage of time, is plainly false. Instead we should focus attention on where pain is inflicted. I have far less problem with human "therapeutic" cloning than I do with, say, the abortion of a 20 week foetus or laboratory experiments on chimps.
Fifty years from now when therapeutic cloning is as common as fixing a dodgy heart valve, people will wonder what all the fuss was about. This is landmark research which can be equated to the discovery of anaesthetics and antibiotics. If it eradicates awful diseases and is managed fairly, therapeutic cloning has got be good news.
Iain Wakefield, Burton on Trent
To those that think opposition to embryonic research is a sign luddism, can I ask whether there is anything beyond their pale? Are all advances good or can we ever go too far? For me this isn't about when an embryo becomes a child or when it gains consciousness or attains a soul or any other emotive religious debates, it's simply a basic ethical question on how we regard human life and existence. In allowing this we have crossed a major line. To prevent this from being abused we should go no further until we have drawn a new clear line.
Philip, London, UK
Clearly few of the people who have 'had their say' understand the cloning process and what they are trying to achieve by it. Growing the embryos up to conscious beings may have ethical implications but that is not what they are trying to do. My only problem is why it wasn't British scientists that made this breakthrough. 'We have managed to cure diseases without this technology up until now' was one comment - well if she knows a cure for my diabetes, please let me know!
Clare, Stirling, UK
There is something Orwellian about the term 'pro-life' in this context. The 'pro-life' brigade would like to ban a technology that may one day provide a cure for diseases such as Alzheimer's or Parkinson's. Banning the technology is likely to mean that more of those patients will suffer agonising deaths. How exactly is that 'pro-life'?
Adam, London, UK
All the arguments about interfering with natural processes and "playing God" simply don't wash. Everyone saying it now is already the beneficiary of previous generations "playing God". It could be argued that the discovery of sanitation was "playing God" because it reduced disease and extended lifespans. We have a chronic shortage of donated organs which could help people, simply because bereaved relatives find it upsetting or improper not to bury or cremate a corpse all in one piece. Let's lose the hypocrisy and encourage what is clearly an important advance in medical science.
Clive, Norwich, UK
There is no doubt that there are apparent benefits to be derived from research of this nature. However, the real problem with technological breakthroughs has never been with the immediate benefits but rather the potential unknown pitfalls in future - a future that science can never predict! Can there ever been a system that completely protects us from misuse of this technology?
Engobo Emeseh, UK
The embryo is only 5 days old when it is cultivated. If we think it is OK to experiment on a grown mouse why can't we cultivate a 5 day old embryo? A mouse is more capable of suffering than an embryo.
Why is it that any expression of caution against science is always met with disparagement of one's religious persuasions? Who really is being intolerant here?
Weri Timi, UK
This is an absolutely disgraceful attempt by scientists to promote themselves whilst undertaking the most sickening procedures. Wrapping it all up in a "worthy cause" does nothing to disguise what is actually happening, which is the purposeful destruction of human beings. No doubt these scientists would be perfectly prepared to undertake such research for a "lesser" cause could they get away with it. So let's not make them into humanitarian heroes, when the murder of countless people is a direct result of there actions. It must stop.
Vanessa bailey, Bristol UK
I think it is despicable that this could have been allowed to happen. Human life is not to be tested upon, it is to be nurtured. This event marks a sad day for Human Rights. The ethics of cloning any species, whether it is human or otherwise, is still in question and should be addressed in the future, instead of being ignored as in this case.
Heather Powell, Reading, UK
Odd that human beings are being treated more like lumps of cells for experimentation whilst animals gain more and more rights. I'm not against the research but the ethical arguments are laughable; scientists do because they can and people want it because they fear disease more than God.
Alastair, W'Ton, UK
I was against this idea for a long time 'till one of my best friends got in a car accident and now that's the only way for her to be back on her feet... I wish I could do something but I don't know whom to get in touch with and till this technology starts working in Russia, she might be gone...
Anna, Volgograd, Russia
Doctors, Surgeons and Scientists have been playing god for too long now. I don't agree with many of the things they now do. Just because we can do something, does not mean we should. Nature is no longer allowed to use its powers of natural selection. Where will it all end?
Bridget, Cambridge, England
It is clear from the points raised so far that there is a massive misunderstanding of the work and its future. Before people condemn this research perhaps they had better inform themselves of the facts first! We're talking about the use of cellular matter that has as much senescence as the banner skin I just discarded for lunch! Embryos are grown for just a few days then the stem cells extracted for use in growing cells and tissues. More advanced embryos are destroyed during IVF treatment which is considered acceptable. Why should the use of embryos to help save lives be worse than the wanton destruction of embryos the are left over after IVF?
Clive McKimmie, Biomedical Scientist, Edinburgh, UK
If it saves lives, it gets my vote.
James, Dorset, UK
When the science behind the atomic bomb was developed, it was hailed as a deterrent to warring factions and an aide to world peace. Ironically, today everyone has them and we're to trying to 'go back in time'. Whilst this breakthrough is quite fantastic, caution and sensible and non-emotive global control must be strictly adhered to.
Farrel, London, UK
A clump of cells on a dish, grown to use for testing, so that animals do not ever need to be tested upon again, are a good step forward in medicine. Eventually science will be able to create better medicine with it, because all the testing is done on human-type test subjects without harming any person with it. Eventually it would even make personalized medication possible, I think. No more swallowing pills and hoping they may work.
Anna Jonkers, Leeuwarden, The Netherlands
Let them continue with this ground-breaking and important research. The cloned embryos are, at the stage being used, just a ball of cells. Yes, given the right conditions, they have the POTENTIAL to become a human being, but by that argument, so does every one of the approximately 420 eggs every woman produced during her life, but we do not deride women for denying most of these eggs the chance of life. Let's get a little perspective here. And in answer to June Neville's question (below) about helping men and older women - every cell in your body (other than red blood cells) contains all the genetic material needed to produce a clone, so the technology has the potential to help all people.
Jill Cockerham, Leeds, UK
I believe this work to be intrinsically wrong and abhorrent. Human beings have been given everything they need to procreate and for the right reasons. We will only create more problems for ourselves through overpopulation and a raft of as yet unknown long term effects of such work. Can't we just accept that the human genome is an area not to be manipulated - are there any ethical boundaries? There are many other areas needing such levels of funding - people who already exist but that are living in terrible circumstances!
Gillian, Northern Ireland
The technology is out there, the potential for curing formerly incurable conditions and relieving human misery is huge. Embryos are only potential human beings after all. Let's get this into perspective. Thousands of far more developed embryos are aborted naturally or by medical intervention every day.
Our daughter was diagnosed with Leukaemia when she was 3. She is now in remission and constantly having regular blood check ups. We know many parents who are not as fortunate as us to still have their children around. Stem cell transplants or bone marrow transplants are a last resort for a cure to diseases such as Leukaemia, and could save the life of children and adults through breakthrough in technologies such as this. If it's used for the right reasons of eradicating diseases which take away life and loved ones - what would you do?
This is an abomination. Stem cells can be harvested from umbilical cords of normal births.
Thomas Swartzwelder DO, Rocky Mount USA
Every advance in medical technology has been greeted with disapproval by some people. Remember the outcry about transplanting organs? There need to be ethical guidelines but the potential for reducing human suffering is enormous.
Muriel Williamson, Skipton, GB
I wonder how you people who are for this technology can sleep at night, knowing that your selfishness resulted in the creation and extermination of another human being. But hey, when all you have to look forward to is this life, you'll do anything in your power to cheat death, including sacrificing another person.
Zach Smith, Bloomington, IN USA
If you accept that the creation and destruction of embryos for IVF treatment is morally acceptable then you should NOT have any problem with this form embryonic manipulation. In fact the embryos used for stem cell work are typically harvested at an earlier, less developed stage than embryos used for IVF related implantation, which are grown for longer in the "test tube". Hence, the Korean scientists have set little new bioethical precedence. The potential positive implications this line of work has for human health is however massive.
Clive McKimmie, Biomedical Scientist, Edinburgh, UK
Don't people realise that Darwin's theory of evolution has stopped for human beings since the advancements of medicine. The human race is 'devolving'. So why should the scientists help to correct this problem?
Richard, Kingston, England
There are many good uses for this technology and so many negative aspects but I can only see this as another example of scientists trying to run before they can walk. All cloning experiments to date have had massive failure rates, we see a few of their successes like Dolly the sheep but she died prematurely due to problems in the cloning process. These problems need to be ironed out completely before we even think about working on human cells.
Richard Scott, Windsor UK
This particular work can only be good. I am against cloning a whole person, but if a human that has been injured in an accident that was caused by somebody else, or has had a disease that has led to the loss of cells in some way, I can only believe that this is a positive thing. Think of all of the instances where children in Africa have lost limbs through land mines, or the Iraqi children that lost limbs recently. Burn victims could have a new skin. Bone marrow could be reproduced for Leukaemia victims. This technology has limitless possibilities for helping people.
Brian Wright, Bristol, UK
Is our love for life or fear of death that is driving this research? Death happens, it is painful for those left behind, but do we really want to stop it?
Rich, Welwyn GC, UK
There needs to be clear ethical guidelines on how this emerging technology is to be used i.e. not for creating a 'perfect race' but for eradicating terminal genetic illness.
The scientists are not killing a child, because the embryo remains unfertilized. All they are doing is transferring the nucleus from a somatic cell into a developing cell in order to make stem cells, which would help patients suffering from all kinds of illnesses including leukaemia and Hodgkinson's disease. They have been doing it in mice for years.
You go tell the crying mother of that child dieing in a hospital bed that you aren't going to save it, just because you have issues with your morals.
Tom, Edinburgh, Scotland
Medical research like this tends to be a complete waste of time and money. Good for careers and charities though. Spend £10m developing a drug that might help 1000 people, or spend £10m on prevention. We all know the links between Lindane and breast cancer - or do we? Is Salmon safe or not? Prevention is the only way forward for mankind - miracle cures are a non-existent nirvana used for personal advancement, not serious healthcare.
Mankind has never developed new "technology" that has not eventually been used to harm and destroy others. If allowed to go on, cloning will be no different.
Erin Leach, Cedarville, USA
Will this research lead to a cure for irrational anti-scientific beliefs? That's what I want to know.
Robert, Zürich, Switzerland
I wish they'd get a move on with the technology. I'd love to have a lie-in and send a clone to the office.
Joe RYAN, Chartres, France
This is a great step in medical science, its a damned shame the luddites and the people who don't have a grasp of any aspect of science will object over this matter.
Andy F, Glasgow, UK
Why is it always the 'nay-sayers' that shout the loudest, when it doesn't really affect them? My mother is about to die from Alzheimer's. Yes it's too late for her, but if stem-cells research can put a stop to this problem, then I'm all for it. What do you think you do in the garden, when you cross-pollinate plants and selectively breed new varieties - is this really that much different? I strongly believe that this type of research is of benefit to all mankind!
Richard Beed, England
All these people saying cloning is playing God and wrong - how do you know? Does it say anywhere in the Bible, Tora, Qu'ran -whatever - "Thou shalt not clone"? Has God personally told you he thinks it's wrong? Do you claim absolute knowledge of His plan for us? Maybe He wants us to become more like him. Until you know, stop whining and let us use science to help the needy.
Ciaran, Durham, UK
I think its brilliant, animal testing has been going on for years and no-one cares that these animals are being robbed of life, it's about time everyone got off their high-horse about human cloning! Abortion clinics should be illegal if people have a problem with humans being "robbed of a future"
I believe that the studying of stem cells is fully acceptable to discover new treatments for some of the planet's worst disorders and illnesses, these stem cells are not at a state of being conscious human beings so I don't see the argument against studying them. I find it unusual more people protest about this type of experiment than you find with women going for an abortion. I think if the people who where so against stem cell research knew someone who had one of these disorders, they would feel more in favour of research in this area.
C Marrow, West Yorkshire
If stem cell research can be used to allay the suffering of people with diseases, then it would seem unethical not to pursue "embryo-cloning".
Henrik Westin, USA
The cells that have been cloned here are simply "building block" cells - nobody is creating anybody to rob of organs or even suggesting such a thing. Once removed these stem cells are no more a living person than your fingernail clippings would be.
Stew, Edinburgh, Scotland
Could cloning be used in cancer treatment - cloning cells from people who have survived cancer?
Life's just a game, and DNA are the pieces with which the game is played. Why shouldn't we be allowed to tamper with them? Playing by the rules takes away all the fun. Nobody knows what life, in essence, is all about, so why should we play by the rules?
I don't have a problem with cloning at all. Medical advances aside, what could be nicer that a planet populated entirely with six billion clones of me?
Scot Kenwood, Poole, UK
These embryos are no more human than the skin cells that you dust off ones ornaments or the sperm that is caught in a condom. Only when something is or once was conscious and self-aware can we possibly consider it to be close to a sentient being. As far as I can see this technology is a wonderful show of human creativity and progression and thus a very cool step forward.
Roland, Chelmsford UK
Either we like it or not cloning is the way forward.
George Nipah, England
My wife is a carrier of the Huntington's disease gene and my children of two and four have a 50% chance of developing the disease in the future. As a husband and father I should be able to protect my family but in this instance I am useless. I fully support all research into hereditary diseases and extend my thanks to all the dedicated scientists around the globe. Keep trying (please)!
Mark Shiner, Southampton, England
I used to be opposed to cloning, until my husband developed Parkinson's Disease. It is a horrid, progressive illness with no cure, which has had a devastating effect on his life, and those around him. I am now totally pro-cloning if it is used to find a cure for Parkinson's and Alzheimer's. Those who are opposed should stop, and think, about those people who are suffering from diseases which now have a potential cure as a result of this research.
People that object to this can fight it out with the animal rights activists. If we can't use humans or animals, what DO we use?
Moo, London, UK
I bet the first people to benefit from this technology will be the people who paid to make it happen. When most people only have access to basic medicines i don't think this will ever be a cure for all. I would therefore support an alternative approach to medicine, regardless of the obvious ethical issues raised by raising embryos for profit.
Eog, Taipei, Taiwan
Why do people always throw in the argument "it's against God's wishes" - has anyone asked him recently then? If this helps to cure disease and illness, then I'm all for it. We're evolving - live with it.
If you have seen a friend or relative suffer from a disease such as Alzheimer's then I think you would understand that if cloning is the only way to cure these diseases then it has to be done.
Mala Shah, Shipley, UK
Creating human embryos for the purpose of destroying them can't be justified - all right; but with the technology in our hands to save millions of lives worldwide, it would be foolish not to use it; The wise decision would be to support such research for the benefit of mankind as a whole.
Rajesh Natarajan, Aberdeen, UK
Both houses of parliament have ALREADY decided this is perfectly OK. It was a free vote, no party politics involved. I can quite understand those with strong views who lost the debate wanting have a second go. Equally I've heard no new information to make me spend a lot of time on the issue. I'll keep listening in case some new thought is aired but otherwise not spent much time worrying about it.
John, Fleet, Hants
As a species we have an instinct to survive. Nature has blessed us with superior intelligence to other animals and we are using it to our advantage. I don't, therefore, worry about the ethics of this science, but I have to admit I am sceptical of it being successful in the long term. I cant help thinking that heart disease, stroke, Cancer etc are all simply mechanisms within nature that control population. Mankind may have to face up to the fact that nature can not be overruled, and that we may never be able to illuminate these conditions, through genetics or otherwise.
Comments about banning cloning (of what are just cells with the potential to form life are understandable), but stopping such research because it's 'playing God' is no better than being forced to believe the world is flat, or that we did not descend from apes. Let's have a rational debate, set the limits based on comment sense and not beliefs, and bring it to countries with high ethical regard rather than push it all to countries where there regards may be far less. If this research can relieve people's suffering, save lives and possibly allow research without using animals, all the better.
Now I am more convinced that the world "ethics" does not exist in business when it comes to any innovation that may generate profit.
Hasan, Guildford, UK
I believe that any use of technology to enhance and lengthen the quality of human life is a worthwhile cause. I for one welcome any advancements that achieve this. Why do some people seem determined for us to stay in the dark ages due to their own individual and, often religious, beliefs. I do, however, strongly advocate the use of stringent controls to ensure that all research is monitored.
Carl Pykett, Coventry
Whether cloning is acceptable or not is something that is sure to be discussed for many years to come, what is certain (and was taught to me in my first year of A-level biology!) is that the structure of DNA begins to change almost immediately due to environmental effects and replication errors (this is one reason why we age). Basically this means the DNA these scientists are harvesting from skin cells to implant into an ovum is damaged and imperfect meaning anything grown from it will likewise be damaged and imperfect.
Dan, Guildford, UK
Human Cloning is always going to be the best way for stem cell research, many babies are terminated for lesser reasons so this should not be an ethical issue, rather an issue of whether it will work or really make a difference.
Matt Smith, Plymouth, Devon
If society is willing to accept that those with the knowledge of how to create human life may use this knowledge to create a source of spare parts from which no doubt great profits will be made, then there will be no boundaries of dignity, morality or humanity that will withstand scientific or corporate greed.
Medicine is not static, and cloning is not necessarily wrong. Until a foetus acquires working BRAIN CELLS it has no more human feeling and right to life than blood taken from my veins. And why shouldn't I store my own blood for a medical procedure?
Durk Trent, Surrey, England
I worry that scientists can't see past their own scientific achievement and development and don't see how their discoveries affect society.
Cat, Cambridge, UK
From the moment fire was discovered people have been afraid of new discoveries and developments. However our nature IS to explore and unravel the unknowns. That is what keeps us going as a race. Taking charge of our own evolution is part of our natural evolution and I am all for it. See opportunities, not obstacles and pitfalls. Imagine what life would be like without fire.
Bart Stefels, Amsterdam, Netherlands
We've sunk to the depths of depravity. Can't anyone admit that life ends? We can't prolong it indefinitely and shouldn't at the expense of the life of another human being.
Ann Muga, Riverview, FL USA
I believe that any use of technology to enhance and lengthen the quality of human life is a worthwhile cause. I for one welcome any advancements that achieve this. Why do some people seem determined for us to stay in the dark ages due to their own individual and, often religious, beliefs? I do, however, strongly advocate the use of stringent controls to ensure that all research is monitored.
Carl Pykett, Coventry
If we can create and then destroy human beings for the benefit of others, who is safe? How do we decide who is valuable, and will be helped, and who is dispensable, and will be destroyed "for the greater good"? I have several severe disabling conditions and use a wheelchair full time. I am in constant severe pain which even morphine cannot completely relieve. Perhaps in theory I could be "helped" by "therapeutic" cloning - but I couldn't live with myself thinking I had been "helped" by cannibalising a fellow human being.
It used to be that your mother told you "you only have one set of eyes" etc. It would be wonderful if we could grow new eyes, nerves, brain tissue, blood cells, hands, pancreatic cells etc. Stem cells are not "babies" and this research is very valuable.
Whilst the intentions of the geneticists may be good, the act itself can only be regarded as a serious negation of human dignity. Every human person created as a means to an end has been robbed of a future, without any choice in the matter. This is something that we should resist as strenuously as possible.
This "therapeutic" cloning is nothing more than creating people to harvest them for their spare parts. Meanwhile, reproductive cloning - an ethically benign (though technically problematic) process that might allow some infertile people to have children - is forbidden and condemned! A classic case of calling good evil and evil good.
Andrew, London, UK
If you refuse to allow a technology because it reminds you uncomfortably of your mortality you've needlessly and pointlessly crippled yourself. These modern-day luddites should realise the potential for this technology and accept that it will happen regardless. You can't stand in the way of scientific advancement.
John Shaw, UK
I think cloning should only be allowed if it is used properly. We should only use it to help stop babies inheriting disease's that are fatal or incurable. You shouldn't be able pick what colour hair or eyes your child has. When you have a baby no matter what it looks like to you it will always be the most beautiful thing you have ever seen.
Amelia, Stoke-On-Trent, England
I believe any advances in this field that can be productively used to eradicate diseases and help humanity should be okay. On the other hand if it becomes another money making enterprise for the rich and stupid, then it should be tightly regulated.
Jim Donovan, Dartmouth, Canada
If the cloning embryos would work as they said it is fine.
Jonathan, Awka, Nigeria
I personally think this is unethical and wrong. Sometimes, it seems scientists tend to play God by tampering with the natural process of creation. For example, Dolly the sheep and all other animal species that were known to be cloned were later discovered to have certain defects. In my opinion, at the end of the day, the end never justifies the means.
Cloning embryos is completely against Gods laws and should not be allowed - they are killing a child
Juliet Mcckellaig, Edinburgh Scotland
Hey, there's a choice - take the medicine or don't. This is really just another example of fanatics trying to impose their beliefs on others who don't share them. Ed, Scotland
Ed Malone, Aberdeen, Scotland
My son was born with a genetic condition called Epidermolysis Bullosa. His skin blisters at the slightest touch and will live his life in constant pain. His ONLY chance of a cure is through stem cell research which may be able to correct the faulty gene that he possesses. If a cure can be found this will help approximately 1 million people around the world and give them a quality of life we take for granted. Let them carry on with the research.
Matthew, Holmes Chapel, UK
There are those who oppose this and claim that they will never use these treatments. What if they have a child who is born with a condition that could be cured by these methods? Can they put their hand on their heart and say that they would rather their child suffered for their whole life rather than cure them immediately with treatment. I'm not so sure.
Tim Spencer, Exeter, England
The potential for therapeutic cloning technology is staggering. The argument that non-sentient bundles of cells (human or otherwise) are somehow sacred is typical of under-informed opinion pushers!
N. C. Doherty, Nottingham, UK
Why not experiment on embryos for stem cell research, after all we've picked on animals who are far more developed for years, why is it more wrong to use our own species to help us than it is to use another? We know the animals in medical research have feeling and can feel pain and discomfort, as well as fear in cages and at the hands of man. So I say let them use embryos, it causes less pain, can be far more useful and has a chance of succeeding.
Will this put an end to testing on live animals? Or will it merely produce another half-educated group of extremist activists?
John Youngs, London UK
If this research becomes a more efficient and reliable replacement to the research currently carried out on primates, I'm all for it. And human embryos are destroyed during IVF processes - how can that be ethical and stem cell research not?
Jan, Edinburgh, Scotland
I think therapeutic cloning is a breakthrough in the treatment of some diseases and must be used for that.
If I remember correctly, it took 234 attempts to produce Dolly the sheep. I DON'T remember any big press coverage or photographs of the first 233 attempts. Why not? Do we REALLY know enough just yet to be sure that we have eliminated all the potential risks?
Chrissie Nyssen, Aberdeen, Scotland
The ethics may still be in question, but they always will be in work of this sort. This is a route that scientists must take in their search for a treatment and cure of many diseases.
Graham Rodhouse, Helmond, The Netherlands
If cloning could have saved my Husband I would have embraced it with open arms
Ruth Bradley, Northamptonshire
Every scientific discovery has the potential to be misused, but the ethical violation occurs in the misuse, not the discovery.
David Hore, Dunedin, New Zealand
We have managed to cure diseases without this technology up until now. Where will it end - growing humans for spare parts! This is an example of technology WITHOUT ethics!
Susan Lucibello, England
To Susan Lucibello - Ethics is irrelevant, the end will justify the mean.
As eggs from the donor are used, presumably for that person, how would this method work with men or older women?
June Neville, Brighton, UK
The central issue at stake here is whether an embryo is conscious, not in the sense of it having this or that cognitive faculty but in the sense of it being like something to be that embryo. If it is conscious in this fundamental sense then the choice whether to continue with therapeutic cloning research or not resembles the choice whether we should eat meat or not or whether we should carry out animal experimentation or not.
Joseph Dormer, Scarborough, UK
Why not? If it will help people, is it any worse than any other medical research?
ARL, Bucks, UK
For or years we have been against experimenting with human clones why the U turn? It is because we can make ourselves live longer they say! Something that will benefit us all! We can all be sat there with nothing to do, penniless, having been forced into early retirement at 50 with a life expectancy of let's say 120. What a great idea! Science without common sense once again!
Justin, Bristol UK
Why should someone be denied the chance of life because someone else thinks the treatment is "unnatural"?
Graeme Phillips, Berlin, Germany (normally UK)
I think it's a magnificent achievement and while some will no doubt criticise this breakthrough we should remember that it could potentially improve the lives of many of those suffering from illness.
Martin Blank, Glasgow, Scotland
This is absolutely, totally wrong. The creation and subsequent destruction of human beings cannot ever be justified. The end never justifies the means. Dehumanisation by changing the noun to describe them does not make them less than human. From a personal perspective I will never use any treatments derived from this abuse of human beings - even if it will result in a reduction of the quality or a shortening of my life.
Phil Smith, Stockport, UK
Is Phil Smith actively looking to have his lifetime reduced?
"I will never use any treatments derived from this abuse of human beings - even if it will result in a reduction of the quality or a shortening of my life." Fine, if he wants to have his quality of life reduced further... Personally I think it is a fantastic breakthrough, if these embryos prove to be viable - there have been many problems in the past with cloned animals. Now we have to wait and see.
James Morell, Bath, UK
When does a human life start? I seem to recall an old philosophy question which asks "If someone throws two things to you at the same time: a box containing a thousand embryos in test tubes, and a baby, which one do you catch?"
Dave, Cambridge UK
I find it hard to believe that we still think we are more important than the animals we experiment on every day. If we do it on animals then why not on humans? We are just animals after all. I for one think that if it has the potential for improving the lives of people with terrible diseases, it should be embraced. In reply to Dave in Cambridge, What an irritating question. Does it even warrant a reply?
Tim, Southampton UK
How will it be ensured that these and other embryos will not be misused? What will be the limits? Who will set the limits? There are still too many open questions.
Eugenia Kothe, Idstein, Germany