[Transgenic mice--biological fundamentals, practices and applications].

The transfer of genes into the germline of mice has become a standard technique of modern biomedical research. In addition to direct microinjection of DNA into the pronuclei of fertilized mouse eggs, genes can now also be inactivated via homologous recombination in embryonic stem cells (gene targeting). In the future it will be possible to inactivate any cloned gene via homologous recombination in ES-cells and establish corresponding mouse mutants.