Quote from //news.nationalgeographic.com/news/2007/10/071008-nobel-medicine.html
U.S. citizens Mario R. Capecchi and Oliver Smithies and Sir Martin J. Evans of Britain won the 2007 Nobel Prize in medicine on Monday for groundbreaking discoveries that led to a technique for manipulating mouse genes.
The widely used process has helped scientists use mice to study heart disease, diabetes, cancer, cystic fibrosis, and other diseases.
They were honored 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.