Transgenic mice: a decade of progress in technology and research

In little more than a decade, the techniques developed for altering the genetic makeup of laboratory and livestock animals and plants have changed the landscape of biological research. It is now possible to introduce virtually any cloned gene into the germ line and study the expression pattern and effects of the introduced gene, or transgene. This has allowed the extension of in vitro and in vivo cell-culture studies into whole animal systems in which the introduced gene is subject to all normal regulatory processes from the onset of development. Although there have been reports of foreign gene expression resulting from direct injection of DNA in animals (e.g., Wolff et al., 1990; Zhu et al., 1993), transgenic animals are the primary model system for examining molecular genetic phenomena in vivo.