They are called mouse archives — facilities around the world in which mice are bred for research. Each has a slightly different genetic alteration so that between the archives, there are mice with almost every gene modified.
Why do this? Well, it is science’s good fortune — though some might say the mouse’s bad luck — that the rodent genome is not that different from its human counterpart.
So when researchers want to study a particular genetic condition affecting humans, they first seek out the mouse with the relevant mutation: wherever that may be. It is a little like a lending library, just with genetically modified animals. As you would expect for a country with a research base the size of Britain’s, all of the