MUTANT MILLIONS: Increasingly exotic bio-engineered mice are created with relative ease these days for research into all manner of diseases.

OF MICE AND MEN: Mice and humans are nearly identical genetically. Each species has roughly 25,000 genes, with just a few hundred genes differing between them.

HOW MANY, HOW MUCH: The U.S. repository for mutant mice boats nearly 3,000 different types and ships 2 million mice a year. A mutant mouse can cost up to $200.