Removing bias in surgical trials

The promise of cloning for human medicineNot a moral threat but an exciting challenge T he production of a sheep clone, Dolly, from an adult somatic cell 1 is a stunning achievement of British science.It also holds great promise for human medicine.Sadly, the media have sensationalised the implications, ignoring the huge potential of this experiment.Accusations that scientists have been working secretively and without the chance for public debate are invalid.Successful cloning was publicised in 1975, 2 and it is over eight years since Prather et al published details of the first piglet clone after nuclear transfer. 3issing from much of the debate about Dolly is recognition that she is not an identical clone.Part of our genetic material comes from the mitochondria in the cytoplasm of the egg.In Dolly's case only the nuclear DNA was transferred.Moreover, we are a product of our nurture as much as our genetic nature.Monovular twins are genetically closer than are artificially produced clones, and no one could deny that such twins have quite separate identities.Dolly's birth provokes fascinating questions.How old is she?Her nuclear DNA gives her potentially adult status, but her mitochondria are those of a newborn.Mitochrondia are important in the aging process because aging is related to acquired mutations in mitochondrial DNA, possibly caused by oxygen damage during an individual's life. 4Experimental nuclear transfer in animals and in human cell lines could help elucidate mechanisms for many of these processes.Equally extraordinary is the question concerning the role of the egg's cytoplasm in mammalian development.Once the quiescent nucleus had been transferred to the recipient egg cell, developmental genes expressed only in very early life were switched on.There are likely to be powerful factors in the cytoplasm of the egg that make this happen.Egg cytoplasm is perhaps the new royal jelly.Studying why and how these genes switch on would give important information about both human development and genetic disease.Research on nuclear transfer into human eggs has immense clinical value.Here is a model for learning more about somatic cell differentiation.If, in due course, we could influence differentiation to give rise to targeted cell types we might generate many tissues of great value in transplantation.These could include skin and blood cells, and possibly neuronal tissue, for the treatment of injury, for bone marrow transplants for leukaemia, and for degenerative diseases such as Parkinson's disease.One problem to be overcome is