UK scientists have applied for permission to create embryos by fusing human DNA with cow eggs.
The hybrid human-bovine embryos would be used for stem cell research and would not be allowed to develop for more than a few days.
But critics say it is unethical and potentially dangerous.
The resulting embryo would be 99.9% human, the only bovine element would be DNA outside the nucleus of the cell.
It would though, technically be a chimera, part-human, part-animal.
clipped from: news.bbc.co.uk