The widely used process has helped scientists use mice to study heart disease, diabetes, cancer, cystic fibrosis and other diseases.

The prize is shared by Mario R Capecchi, 70, of the University of Utah in Salt Lake City; Oliver Smithies, 82, a native of Britain now at University of North Carolina in Chapel Hill, and Sir Martin J. Evans, 66, of Cardiff University in Wales.

The Nobel is a particularly striking achievement for Capecchi, a native of Italy who at the age of 4 was separated from his mother when the Gestapo took her to the Dachau concentration camp during World War II. Capecchi lived on the streets for more than four years, fending for himself by begging and stealing, until reuniting with his mother at the age of 9. They soon moved to the United States, where he started elementary school without knowing how to read or write, nor how to speak English.

The three scientists were honoured for a technique called gene targeting, which lets scientists inactivate or modify particular genes in mice. That in turn lets them study how those genes affect health and disease. To use this technique, researchers introduce a genetic change into mouse embryonic stem cells. These cells are then injected into mouse embryos. The mice born from these embryos are bred with others, to produce offspring with altered genes.

More than 10,000 different genes in mice have been studied with the technique, the Nobel committee said. In a telephone interview from Salt Lake City, Capecchi called the award “a fantastic surprise”, while Smithies said getting the award was “very gratifying”.

Capecchi’s work has uncovered the roles of genes involved in organ development in mammals, the committee said.

Evans has developed strains of gene-altered mice to study cystic fibrosis, and Smithies has created strains to study such conditions as high blood pressure and heart disease.