Credit: JACKSON LAB

Compared with the media frenzy that greeted the publication of the human genome, coverage of the draft mouse sequence, unveiled this month1, was a relatively sedate affair. But for many scientists, the mouse genome deserves at least equal billing, as it provides the key to unlock the secrets of our own DNA.

The two genomes, it turns out, are remarkably similar: 99% of mouse genes have a direct human counterpart. It is not a unique set of genes that make us human rather than murine, but rather the way that they are regulated.

On one level, this humbling similarity exposes the daunting complexity of mammalian biology. But it also means that the mouse — newly named as man's best friend — is here to help promote our self-knowledge, and to spur medical advances.

Armies of mutant mice are being created to study human diseases, and to understand myriad aspects of our biology. Molecular tools to interpret sequences are also being developed apace. For instance, a new set of mouse complementary DNA clones2 will make it easier to investigate gene function by generating 'knockout' mice.

What next? Another team has already posted on the Internet a preliminary assembly of the rat genome3, and a peer-reviewed publication should follow next year. This is good news for physiologists, for whom the rat is the favourite experimental animal.