New York City ? As a child in Italy during World War II, he lived for years on the streets and in orphanages. Six decades later, as a scientist in the United States, Mario Capecchi joined two other researchers in winning the Nobel Prize in medicine.

Their work led to a powerful and widely used technique to manipulate genes in mice, which has helped scientists study heart disease, diabetes, cancer, cystic fibrosis and other diseases.

The $1.54 million prize was awarded Monday to 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.

Their “gene-targeting” technique lets scientists deactivate or modify individual genes in mice and observe how those changes affect the animals. That in turn gives clues about what those genes do in human health and disease.

The work has had “a revolutionary effect on the ability to understand how genes work,” said Richard Woychik, director of The Jackson Laboratory in Bar Harbor, Maine, a center for mouse genetics.