Safety, it turns out, is the major rub. The human cloning process reported this week would not produce embryos that would lead to a viable pregnancy, says Shoukhrat Mitalipov of Oregon Health & Science University in Beaverton, who headed the Cell report team. A similar process in monkey cells didn't, he says, indicating that the fusing process disrupts the potential for pregnancy, even while it creates embryos that can produce stem cells.
But that doesn't mean someone won't try, which worries stem cell scientist Paul Knoepfler of the University of California-Davis. "Also, with some tinkering, I'm betting someone somewhere is going to get it to work in the next few years, or at least try to do it and fail," he says. That could mean developmentally disabled or otherwise sick babies born, as a result. "I hope I'm wrong," he adds.
Why are some worried? Because most cloning attempts in mammals, more than 90%, end in miscarriages, and many of the ones born alive suffer from severe health defects. "About a third of the cloned calves born alive have died young, and many of them were abnormally large," notes the Energy Department's Human Genome Project office. USA TODAY