Knockout mouse

A knockout mouse is a genetically engineered mouse that carries one or more genes in its chromosomes that has been made inoperable or "knocked out." Knockout is a route to learning about a gene that has been sequenced but has an unknown or incompletely known function. Knockout mice are frequently used in drug development as a test of the potential for a particular human enzyme as a target for therapy. Identical or nearly identical versions of most human proteins exist also in mice. Knocking out the gene that encodess the related enzyme in mice enables researcher to mimic the effect of inhibiting it with a drug, even before an appropriate drug has been discovered. Mice are the laboratory animal species most closely related to humans in which the knockout technique can be easily performed, so they are a favorite subject for knockout experiments, especially with regard to genetic questions that relate to human physiology.