Genetically Modified Organisms

Although humans have altered the characteristics of many other species over the years (most notably in plant and animal domestication), a watershed was reached in the early 1970s when biologists began to directly manipulate DNA. This “genetic modification” or “genetic engineering” involved altering, recombining, and transferring genes from disparate organisms. It is one of the most powerful [Page 738]technologies ever devised; it is also one of the most controversial because of the ethical, legal, political, economic, and biological issues it raises.

Even the basic vocabulary for the subject is contested. The term genetically modification first appeared in the 1970s to describe early experiments on bacteria. But by the 1990s, in response to portrayals of such creations as sinister and unnatural, some proponents began to label all domesticated crops as “genetically modified” since ancient farmers had modified the plant's genetic makeup. The term genetic engineering, preferred by some biologists, is resented by some engineers because of the uncontrolled aspects of the process. Transgenic is often used for organisms with recombinant DNA, although it is not strictly accurate in cases where an organism's own genes have been altered. Genetically Modified Organism (GMO) here refers to an organism containing genes that have been directly manipulated.

The biology of genetic modification traces to work in the 1950s showing that bacteria exchanged genetic material in the form of extrachromosomal rings called plasmids. In the late 1960s, biologists learned to use the “restriction enzymes” that bacteria use to cut up the DNA of attacking viruses; these enzymes could be wielded to cut specific genes out of DNA molecules. In 1972, Paul Berg succeeded in making a recombinant plasmid, or gene construct, containing cut sections of DNA. In 1973, a team led by Stanley Cohen and Herbert Boyer inserted a recombinant plasmid into an E. coli bacterium, making it the world's first GMO; this allowed the production of large numbers of the plasmids, which could then be used to modify different organisms.