Introduction: Strategies for developing genetically modified mice.

Advancements in transgenic technologies have made the mouse one of the most useful animal models for biomedical research. Several technological breakthroughs have allowed the generation transgenic and knockout mouse models some 25 years ago. Subsequently, the technology has undergone many improvements, advancing our ability to control the expression of the genes and determine the cell types where the genetic modification should take place. Hence, the mouse is unique in offering the possibility to understand genotype-phenotype relationships that are relevant for unraveling the biological role of these genes in the human. This chapter provides an introductory overview.