Manipulating mammalian genome by gene targeting

The development of strategies which allow the inactivation of specific muri ne genes by homologous recombination in embryonic cells has revolutionized biological science in the last 10 years. A large number of mice carrying ge netic lesions, generated by gene targeting technology, has tremendously inc reased our knowledge in many areas of biology, culminating in the identific ation of mouse models for human genetic disorders. These findings have been recently complemented by "conditional" gene targeting technology, allowing gene inactivation in a defined tissue and at a specific time point during development or adulthood, thereby extending the sophistication and potentia l of this technology.