Because mice are so closely related to humans—relative to other common lab animals—they are particularly suited for investigations of human genetics. Researchers today rely heavily on “knockout mice,” mice that have been bred with one or more genes intentionally switched off. Millions of these mice are used each year in studies of aging, cancer, obesity, and other conditions. So prized are they that some strains of knockout mice have even been patented. When was the first knockout mouse created? Discuss