Dolly (R), the first cloned sheep produced through nuclear transfer from differentiated adult sheep cells, and Polly, the world's first transgenic lamb, in their pen at the Roslin Institute in Edinburgh, Scotland, 1997. Polly was cloned with a human gene so that her milk would contain a blood clotting protein that can be extracted for use in treating human hemophilia.
(AP Photo/John Chadwick)
