Researchers from the Roslin Institute in Edinburgh, Scotland, broke an embargo this weekend to disclose that they have successfully cloned a sheep from an adult cell, something that many researchers had believed couldn't be done. The research was to be disclosed in Nature later this week.

The work builds on previous efforts by the scientists. Last March, Roslin researchers reported that they had successfully cloned sheep by transferring the nuclei from cultured cells taken from sheep embryos into oocytes