JOHN CHADWICK/ASSOCIATED PRESS
Dolly, right, the first cloned sheep produced through nuclear transfer from differentiated adult sheep cells, and Polly, the world's first transgenic lamb, are in their pen in Scotland, in early December, 1997. Scientists at the Roslin Institute produced Molly and Polly cloned with a human gene so that their milk will contain a blood clotting protein that can be extracted for use in treating human hemophilia. Dr. Ian Wilmut's technique motivated many governments to ban research on human cloning. Dolly was later naturally mated and gave birth to a healthy lamb.