The connective cells, known as fibroblasts, are then isolated and an electrical current is used to force-feed them with the snippets of DNA that make factor VIII.

BBC: Genetics work eases haemophilia

But scientists from three hospitals in Boston, USA, found that they could temporarily reverse the effects by extracting skin cells from patients whose DNA can't make factor VIII.

BBC: Genetics work eases haemophilia

And in two of these patients the factor VIII levels were high enough to bring the level of their disease from "severe" to either "mild or moderate" haemophilia.

BBC: Genetics work eases haemophilia