In 1996, Ian Wilmut, Keith Campbell, and their colleagues at Roslin Institute and PPL Therapeutics in Scotland cloned a sheep named Dolly. Dolly—the first mammal to be cloned from a single adult cell—sparked a heated controversy. Although most people are concerned about the ethics of human cloning, others worry about how cloning will impact animals. One area of particular concern is “pharming,” a process whereby farm animals are made to produce medically useful compounds such as the enzyme AAT, which is used to treat the lungs of patients with emphysema. Cloning would finally enable scientists to make copies of such genetically altered animals—called transgenics—in order to produce such compounds more efficiently.

Proponents of pharming contend that it could benefit human health. For example, Ian Wilmut claims that the human protein...