Mouse code laid bare

The genetic make-up of the mouse has been laid bare by a publicly funded team of international scientists.

The information will prove crucial to researchers investigating the human genome, the complete set of biochemical instructions used by cells to build and maintain our bodies.

It is remarkable that we were able to complete the mouse genome in such a short time and with such great accuracy

Dr Robert Waterston

Comparing the mouse and human genomes will help scientists better understand how our cells work and why we get ill when one or more of our genes malfunction.

"The mouse is a key model organism for humans," the Sanger Institute's Dr Tim Hubbard, one of the lead researchers on the project, told BBC News Online.

"Their genomes are so similar that you can just compare the two directly. If there are mouse genes we know something about, we can now find genes that look the same in humans."

Some refinement

The mouse data have been produced by a number of US and UK institutions, funded by the National Institutes of Health in America and the Wellcome Trust in Britain.

Although a private US company has already read the mouse genome, its research is not freely available to the world's scientists - they must pay for access.

In contrast, the work done by the international Mouse Genome Sequencing Consortium has been posted openly on the net. Anyone can browse and use the information.

The work is not quite complete. About 4% of the genome still needs to be determined and researchers say further proofing of the current "draft" assembly will inevitably lead to some refinement.

Nevertheless, the consortium is delighted with its effort and the speed with which the job has been done. It has only taken about a year.

Similar numbers

"It is remarkable that we were able to complete the mouse genome in such a short time and with such great accuracy," said Dr Robert Waterston, from the Washington University School of Medicine in St Louis, one of the main institutions involved in the project.

The mouse has a fantastic sense of smell and you can already see that in the genes

Dr Tim Hubbard

"We are now working hard with an international group of experts to explore the content of the sequence and to use it to improve our understanding of the human sequence."

The mouse genome is bundled into 20 chromosome pairs and the current analysis suggests that it is about 2.7 billion base pairs, or "letters", in size.

This makes it slightly smaller than the human genome, which has about 3.2 billion base pairs spread out over 23 pairs of chromosomes.

The analysis also suggests the rodent has about 30,000 genes, a figure broadly similar to humans.

Sick mice

"The mouse has a fantastic sense of smell and you can already see that in the genes," said Dr Hubbard, who has been analysing the DNA sequence at the European Bioinformatics Institute in Cambridge, UK.

"It has a lot more genes than humans connected with olfactory receptors.

"So, the animal has its specialities and even looking at those differences will help us understand those things which are critical to humans that mice don't have. But the basic biology, the basic physiology, is very similar to humans, and having this new information is going to consolidate our understanding of what are the key parts for making a vertebrate."

Scientists can work out what human genes do by "knocking out" similar looking genes in mice and studying the results.

Researchers can also trace the malfunctioning genes responsible for disease by examining sick mice that display symptoms apparently similar to human conditions.

Famous anniversary

With the help of the mouse data, scientists should now finish completely their decoding of the human genome by April next year - just in time for the 50th anniversary of Crick and Watson's discovery of the helical structure of DNA.

Analysis of the mouse data also confirm researchers' initial assessment that humans have somewhere in the region of 30,000 genes.

This figure came as a surprise to many people when it was announced last year - some thought the more sophisticated an animal was, the higher would be its gene count.

Genome studies now show that sophistication in an organism comes from the way its genes interact.