Description: (Applicant's Description) Increasingly both transgenic and knockout mice are being used in cancer research to model gene amplification and emulate loss of tumor suppressor gene function. Moreover these reagents are emerging as highly relevant systems to test novel chemopreventive or chemotherapeutic drugs. An overriding goal of the Transgenic/Targeted Mutagenesis Core is to be at the forefront of translational cancer research. As such transgenic and knockout mice are logical and necessary extensions of investigations begun in cell culture, prior to applications to clinical investigations. The overall goals of this Core Facility will be production of transgenic founder and knockout chimera mice for the University of California San Francisco Cancer Center. In addition the Core will provide "modular" services such as embryo rederivation, embryo freezing, and standardized embryonic stem cells for gene targeting for laboratories with in-house expertise. Moreover the Core will be dedicated to optimizing emerging techniques of murine genetic manipulation such as aggregation techniques for chimera production, and production of standardized transgenic lines for both inducible gene expression, and tissue specific knockouts.