Tuesday, December 8, 1998 Published at 14:34 GMT
The emerging cell technologies
Animal-cell experiments have shown promise
What is a clone?
A clone is a group of cells or an organism that comes from a single "parent" individual and has exactly the same genetic make-up. Cloning is not a man-made phenomenon - several organisms such as bacteria clone themselves as a way of reproducing.
A human fertilised egg can also, quite naturally, split to produce two embryos. These identical twins are, by this definition, clones.
So what has changed?
Scientists showed with Dolly the Sheep that they can take the genetic material from an adult animal and implant it into an empty egg which will then develop into a normal foetus once inside the womb of a surrogate mother.
As with Dolly, the embryo is identical to its genetic parent. This "nuclear transfer" technique could, in theory, be used to clone an adult human. However, for ethical reasons, no mainstream scientist has declared any interest in pursuing such research.
What have the government's genetics advisors recommended?
The joint report from the Human Genetics Advisory Commission (HGAC) and the Human Fertilisation and Embryology Authority (HFEA) states that any attempt to create a full human clone should be outlawed. But they make a distinction between reproductive cloning - the creation of an identical living human - and what is termed therapeutic cloning. This would involve the cloning of cells for use in transplants and other medical treatments.
How would this work?
Adult or infant cells would be cloned to produce an early-stage embryo - a clump of probably no more than about 40 cells. Scientists would then isolate and grow-up from this clump the so-called stem cells.
These are the "master cells" that have the capacity to become any of the tissues in the body. When the technology has been developed - and it is still some way off - these stem cells could be directed to become specific tissues that could then be used for therapeutic purposes.
What sort of treatments?
There are a variety of human diseases that are caused by the death or dysfunction of just one or a few cells. In juvenile-onset diabetes, a particular cell in the pancreas dies. In leukaemia, a specific blood cell becomes malignant. The intention is to replace these damaged cells with healthy copies grown-up from the stem cells isolated from the clone.
What is more, because the cells are clones of the patient's own cells, they will not be rejected as foreign - a problem that bedevils current transplant treatments. Remember that - unlike skin cells - many cells do not easily divide and replace themselves. When nerve cells and heart cells die, that is it - they have gone. This technology gives us the potential to replace failed tissues. Hence, the exciting list of possible applications: heart disease, spinal cord injuries, Parkinson's disease, etc.
Is this what is meant by "spare-part" technology?
If you mean the creation of specific cells for the replacement of damaged ones, then the answer is yes. If you mean the creation of a whole organ such as a liver or a heart on a lab bench, keep reading the science fiction novels.
Even if scientists learn how to control and direct the development of stem cells, it is unlikely - certainly in the short to medium term - that they could control the process of cell division such that they could grow a whole organ. It would require many support technologies that simply do not exist.
An alternative would be to produce a cloned human whose sole reason for existence would be to act as a "warehouse" of spare parts for use by the genetic parent, but society would regard this as ethically unacceptable. The HGAC and the HFEA have given such an idea short shrift.
But isn't any form of cloning going to be a slippery slope?
It is really down to all of us to decide what eventually happens. The cloning and stem-cell technologies are in their infancy. Early work on animals - particularly with mice - have shown that the sort of treatments mentioned above should be possible.
However, society must decide, through parliament and its statutory regulatory bodies, what is permissible. The HGAC and HFEA recommendations are part of that process. But, yes, it is always possible that a rogue individual will want to break the limits set by society.
The maverick American biologist Dr Richard Seed has already announced that he intends to use the Dolly technology to create a human clone. He is going to set up a base in Japan where the laws do not prohibit such research.