The Transgenic Gene-Targeting Core has been an integral part of the Gladstone Institutes UCSF research community for more than 15 years, producing essential mouse models as a service to Gladstone investigators and UCSF faculty. To generate a transgenic mouse, a fragment of DNA is injected through a glass needle into a pronucleus of a fertilized one-cell host embryo. Microinjected embryos are implanted into oviducts of recipient female mice to permit development of the embryos into new lines of “transgenic” animals with the foreign DNA incorporated into their genomes. The foreign DNA can be designed to contain a functional gene that produces a particular protein or modulates the expression of host genes. This technology enables investigators to learn how specific genes and proteins, or their variants, function in a natural living animal environment with a defined genetic background in ways not possible by other experimental approaches. At the Gladstone Institutes transgenic mouse models have been used to understand how specific genes affect atherosclerosis, Alzheimer's disease, obesity, AIDS, and other diseases and disorders that impact modern life.