Thursday, June 17, 1999 Published at 11:45 GMT 12:45 UK
First cloned human embryo revealed
The first cloned human embryo: a collection of stem cells produced using nuclear transfer
Details of the first human embryo to be cloned have been released.
The watershed achievement in biotechnology actually happened last November, but more information was revealed on Thursday. It was achieved using a cell from a man's leg and a cow's egg.
The scientists who created the clone see it as a significant step forward in the search for a way of producing human stem cells.
These are "master" cells which can develop into any type of cell - skin, bone, blood etc. They are believed to have the potential to provide perfect-match tissue for transplantation and the treatment of diseases such as Parkinson's and stroke.
But this development will also see a significant heightening of the debate over the ethics of human cloning and, indeed, what it means to be a human.
American Cell Technology (ACT), a leading, private biotechnology company, cloned the first human embryo and let it develop for twelve days before destroying it. In a normal pregancy, an embryo implants into the womb wall after 14 days.
Dr Robert Lanza, ACT's director of tissue engineering, told the Daily Mail newspaper that the embryo cannot be seen as a person before 14 days. The company say they have released news of the discovery to try to allay fears over the artificial conception of life.
"Nuclear transfer" cloning requires the egg to be hollowed out
It is believed that many more human embryos have been created and destroyed since November. Then it was announced that stem cells had been cloned, not that embryos had been allowed to develop.
No cloned children
ACT say they have no intention of attempting to use a cloned human embryo to start a pregnancy - their aim is "therapeutic cloning" not "reproductive cloning".
Lord Robert Winston, a British fertility expert, said the research was "totally ethical".
But opponents say that the development of the technology makes the eventual birth of a human clone inevitable. This, they say, would have profound implications for the nature of family relationships, the law and health.
The technology used to create the clone was very similar to that used to make Dolly the Sheep. Over 200 embryos were used before Dolly finally appeared, showing that cloning is not a well-understood or easy-to-perform technique.
It is understood that ACT used a cow's egg. This had its DNA removed and replaced with human DNA. The new cell was then chemically persuaded to behave like a new embryo and start dividing. This is how ACT hope to cultivate stem cells.
But Dr Maisam Mitalipova, a pioneer of this human-cow type of cloning, told the Daily Mail: "We didn't get good quality embryos and so they may not get good quality stem cells."
Another US company, Geron, are also reported to be attempting to clone human embryos for therapeutic purposes.
They recently bought all the shares in Roslin Bio-Med, a company set up to commercialise the cloning expertise of the Roslin Institute, Scotland, where Dolly the sheep was created.
Geron has not publicly stated whether their attempts have been successful and it may be that ACT have acheived the feat first.