Transgenic organisms are created by engineering their native genetic material so it carries pieces of genetic material from another organism or breed. A wide collection of techniques are used to create transgenic animals, plants, bacteria, and viruses, including recombinant DNA techniques common in most molecular biology labs. The most common types of transgenic organisms are bacteria and viruses capable of accepting DNA for the purpose of replicating it. Antibiotic resistance genes are routinely used in bacteria as markers for the presence of plasmids carrying transgenes. Applications of transgenic bacteria and viruses include cloning DNA for the production of proteins, chimeric molecules, and vaccines.

The practice of cutting, pasting, and copying DNA originated with Arthur Kornbergs discovery of DNA polymerase and the replication of viral DNA in 1967. This was followed with research by Stewart Linn and Werner Arber who found that restriction enzymes in bacteria can degrade foreign viral DNA molecules without affecting their own DNA. As the development of recombinant DNA tools and techniques advanced, concern grew over the potential danger of genetically modified organisms that could be released into the wild with unknown or dangerous properties. A voluntary moratorium in 1974 and the Asilomar Conference in 1975 were some of the first steps taken by the scientific community to address these concerns. The resulting guidelines for recombinant DNA work and the establishment of the Recombinant DNA Advisory Committee (RAC) were intended to satisfy the public that precautions would be taken to control these powerful new technologies.

Recombinant DNA techniques became more commonplace after a series of pivotal milestones in biological research, including the discovery of restriction enzymes and ligases, the first DNA sequencing, the discovery of reverse transcriptase, and the invention of polymerase chain reaction (PCR). The first transgenic mouse was made in 1974 by Rudy Jaenisch and Beatrice Mintz, but the first transgenic mice capable of passing foreign DNA onto their offspring were not made until 1981.