Introduction to Transgenesis

Over the past decade, a number of techniques have been developed that allow the introduction of defined, cloned DNA sequences into animal germ lines. Once inserted, these sequences, now called transgenes, are stably passed on from generation to generation. In other words, the transgene becomes a part of the genetic make-up of that particular line of animal. Every individual of a particular line will carry the transgene in every cell of its body. Of fundamental importance has been the observation that transgenes are often expressed—that is they are functional—and that this expression is subject to correct tissue-specific, developmental, and physiological regulation. It is therefore now possible to analyze the role and regulation of specific cloned genes within the whole organism. Such organisms are called transgenic organisms.