Scientists sequenced the complete mouse genome in an effort to understand the differences between the human genome and the genome of a mouse.
Mice are widely used as experimental models in laboratories worldwide.
Humans and mice have four-fifths of their genes in common, which directly enhances scientists' abilities to pick out mouse genes that are most applicable to human disease.
In the first comprehensive comparison between the genes of mice and humans, scientists from America, Sweden and the UK have found that there are more genetic differences between the two species than had been previously thought.
The team has discovered a vast treasury of new genes and many of these are evolving at an unusually rapid pace, probably as a result of an evolutionary 'arms race' among mice and their reproductive cells.
"In retrospect, our previous picture of the mouse genome was incomplete. Only when all the missing pieces of the genomic puzzle had been filled in did we realize that we had been missing large numbers of genes found only in mice, and not in humans," said Dr. Leo Goodstadt from the MRC Functional Genomics Unit.
"These new findings are extremely important in helping us to separate genes that underpin biology that is the same across all mammals, from genes that make humans and mice so different from one another," said Prof Chris Ponting, from University of Oxford, UK, one of the leaders on this project.
"With the benefit of hindsight, we now see how incomplete our initial summary of the mouse genome was," said Dr Deanna Church, National Center for Biotechnology Information at the US National Institutes of Health, who also led the project.
"The painstaking work to complete it has been well worthwhile. The new findings will allow us to dismiss some commonly held misconceptions and, more importantly, to reveal many previously hidden secrets of mouse biology," Church added.
The study appears in PLoS Biology.