A British researcher is one of three scientists to share this year's Nobel prize for medicine for work on genetically altered mice that leading scientists say is revolutionising treatment of serious illnesses.

Sir Martin Evans, professor of mammalian genetics at Cardiff University, played a key role in the creation of the genetically engineered animals that are used as models for human diseases.

Commonly known as "knockout mice", these rodents have key genes deliberately inactivated or silenced, in order to mimic certain illnesses. The rodents are now used throughout biomedicine, from basic research into human diseases to the development of new treatments.

Using the technique, mice have been bred with medical conditions ranging

from cancer to heart disease and cystic fibrosis. So far, scientists have "knocked out" more than 10,000 mouse genes.

Sir Martin, 66, shares the £755,000 Nobel prize in physiology or medicine with two naturalised Americans, British-born Professor Oliver Smithies, from the University of North Carolina, and Italian-born Professor Mario Capecchi, from the University of Utah.

Together they made a series of ground-breaking discoveries involving the

manipulation and disabling of mouse genes. Sir Martin's chief contribution was identifying embryonic stem cells and using them to deliver genetic changes to the animals.

A statement from the Nobel Assembly at the Karolinska Institute in Sweden, which awards the Nobel prizes, said: "In summary, gene targeting in mice has pervaded all fields of biomedicine. Its impact on the understanding of gene function and its benefits to mankind will continue to increase over many years to come."

Leading scientists also hailed this year's winners. Professor Stephen O'Rahilly, Head of the Department of Clinical Biochemistry at University of Cambridge said: "The development of gene targeting technology in the mouse has had a profound influence on medical research. Thanks to this technology we have a much better understanding of the function of specific genes in pathways in the whole organism and a greater ability to predict whether drugs acting on those pathways are likely to have beneficial effects in disease."

Professor Paul Sharpe, Head of Craniofacial Development at King's College

London added: "The impact of their pioneering work cannot be overstated since it changed the way all areas of mammalian biology and medicine are studied."

The Nobel Prize in Physiology or Medicine is the first of six prestigious Nobel awards to be announced this year. The others are for chemistry, physics, literature, peace and economics.