In Provo, Utah...

British scientists are seeking permission to create hybrid embryos in the lab by fusing human cells with rabbit eggs. If granted consent, the team will use the embryos to produce stem cells that carry genetic defects, in the hope that studying them will help understand the complex mechanisms behind incurable human diseases.

"The fertility of rabbits is legendary," said Prof Shaw. "The most important thing is that with animal eggs, we have a much better chance of generating stem cells and if we wait for human eggs, it's going to be maybe a decade before we can do this. If we can use animal eggs, we could maybe have stem cells within one or two years," he added.