Enlarge ImageBad programming. These hybrid embryos, in which human DNA has been placed in animal eggs, don't turn on the same genes as human embryos. Credit: ACT/Cloning and Stem Cells Can a person be cloned? And can human-animal hybrid embryos produce stem cells that shed light on human diseases? "Probably" and "no" are the respective answers to these provocative questions, according to a study out today. Ever since researchers cloned Dolly the sheep in 1996 by transferring the nucleus of one of her cells into the nucleus-free egg of another sheep, scientists, ethicists, politicians, and the public have wondered...