[Transgenic animals: uses and limitations in the 21st century medicine]

One of the most important advances in biotechnology during the last decades was the development of transgenic animals. In this article, I discuss why transgenic animals are excellent models to analyze gen function and regulation, and to look for new therapeutic strategies for human diseases. Moreover, their use as bioreactors to produce pharmaceutical products for the treatment of human diseases, and the possibility of generating transgenic pigs as an alternative source of organ donors for humans is also discussed.