"The cloning of Dolly in 1996 from the cell of an adult sheep was a pivotal moment in history." "In this definitive account, the scientists who accomplished this stunning feat explain their hypotheses and experiments, their conclusions, and the implications of their work. Researchers have already incorporated into sheep the gene for human factor IX, a blood-clotting protein used to treat hemophilia. In the future, cultures of mammary cells may prove to be valuable donor material, and genetically modified animal organs may be transplanted into humans." "But what are the ethical issues raised by this pioneering research, and how are we to reconcile them with the enormous possibilities?"--Jacket.