The issue of cloning and embryonic stem cell research intersect when it comes to possible uses of cloned tissue as a source of stem cells.

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Dr Frisen reckons that they may offer several advantages over human embryonic stem cells which, although easier to manipulate, are a controversial source of new tissue because they are still mainly obtained from aborted fetuses.

ECONOMIST: Stem cells

As the source of every cell, tissue and organ in the body, their medical application has the potential to repair damaged tissue, regrow internal organs and cure currently incurable diseases like cystic fibrosis, Alzheimer's and Parkinson's.

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However, he said that embryonic stem cells remained the most obvious source of cells for such transplants, as foetal tissue - used in some experiments - was scarce, and so-called "adult stem cells" had never been converted into the right type of brain cells, despite 15 years of research.

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