A new £18m animal testing centre to examine the genetic make-up of mice and humans has been opened.
Mice and humans are genetically very similar, say scientists
The Mary Lyon Centre, at Harwell in Oxfordshire, will house 65,000 mice.
Scientists want to discover how genes contribute to disease and are focusing their research on mice because they are genetically very similar to humans.
One animal rights group described the centre as "a massive step in the wrong direction", claiming the results of animal testing are often misleading.
Part of the research will consist of placing new genes in the mice and mutating existing genes to see if the rodents become more resistant to disease.
The biochemical "life codes" of both humans and mice have now been laid bare, and scientists believe that by running genetic tests on rodents they can get closer to understanding the causes of disease in humans - and how to find new treatments.
Professor Steve Brown, director of the Medical Research Council's (MRC) Mammalian Genetics Unit, said: "One of the major challenges for the 21st Century is to determine the function of all genes in the mammalian genome and their role in human disease.
"The Mary Lyon Centre with its state-of-the-art facilities and expertise will make an enormous contribution in achieving this goal."
'Leaps in understanding'
Professor Colin Blakemore, chief executive of the MRC, said: "If it hadn't been for research involving mice, we wouldn't have made such leaps in understanding - the cause of cystic fibrosis and certain types of deafness, the improvements in treatments for depression, the advances in treatments for some cancers, or as much progress in the development of vaccines for tuberculosis and malaria.
"The Mary Lyon Centre will help ensure that medical research continues to make groundbreaking contributions towards the improvement of public health."
But Andrew Butler, from Peta (People for Ethical Treatment of Animals) said: "This is a massive step in the wrong direction as any other animal rights group in the UK would agree.
"Animal testing is known to produce wildly misleading and erroneous results.
"What we need in this country is real investment in alternative procedures. We need a dedicated centre to fund, seek out and validate non-animal research."