Genetically engineered livestock are producing human proteins in Scotland. A Schnieke and his colleagues at PPL Therapeutics, Roslin, Midlothian, Scotland, have developed the sheep following their success of cloning Dolly, the world first clone of an adult mammal. The cloned animals have a gene that produces a human blood coagulant in their milk. They express human factor IX that is used to treat haemophilia. Such animals may become an important source of medicines in future.