With the identification of genes proceeding quickly among a number of companies, the current challenge in biology is centered on understanding the function of the 100,000 or so human genes involved in normal development and the role any given gene may play in disease. But ascribing function to any particular gene has proved to be a far slower process, and only a small number of sequences - a few percent - have been functionally defined. The upshot is that the evolution of potential therapeutic targets has seriously lagged the sequencing process.

Hexagen plc's answer to the problem is to create custom-designed mice. The company is building a colony of 10,000 mice that will be subjected to chemical mutagenesis to induce random mutations that can be used to discover the function of genes of interest. A variety of mutations will provide a variety of outcomes, making it possible to study the range of disease phenotypes associated with the target gene.