Mice have been freeloading on humans for millennia. Now, in laboratories around the world, scientists are returning the favor. Model systems such as the fruit fly Drosophila melanogaster and the nematode Caenorhabditis elegans are actually easier to work with than mice, but mice are more closely related to humans, making them better models of human physiology. "For modeling genetic diseases like breast cancer, you definitely need mammals," says Kay-Uwe Wagner, a molecular biologist at the Eppley Institute for Research in Cancer and Allied Diseases, Omaha, Neb.
Early in the 20th century, geneticists used inbred mouse strains for much of their work.1 Long before the true nature of a gene was understood, geneticists were using inbred mice--genetically identical animals, akin to identical twins--to map murine genes. These early mice had other uses, too: they served as xenograft hosts and helped researchers tease apart the nuances of the immune system.
In the ...
