Ultimately, these advancements led to the discovery of deoxyribonucleic acid (DNA) in the early 1950s as the source material of all genetics. Shortly thereafter, James Watson and Francis Crick first determined the structure of DNA. The discovery of DNA's structure made possible the direct manipulation of genetic traits.
Techniques for the insertion of foreign genes into bacteria were first developed in the early 1970s by several laboratories at various universities, including the University of California at San Francisco, Stanford University, and Harvard University. These developments set the stage for the biotechnology revolution to come.
The first product of modern biotechnology made use of insulin, a protein hormone produced in the pancreas that the body uses to regulate the concentration of blood sugar (glucose). Diabetes patients can no longer produce insulin, and must rely on an outside source to adequately regulate blood glucose.
Insulin was first isolated from the pancreases of cows and pigs in the early 1920s. This animal source of insulin proved effective for the treatment of humans with diabetes, and was soon available to patients. Because the animal insulin was not identical to the human material, however, physicians became increasingly concerned with the effects of its long-term use. Furthermore, as the population of diabetic patients continued to grow the mid-1970s, there was considerable concern about the long-term supply of insulin from animal sources.
These factors made insulin an ideal target for a small group of biochemists and molecular biologists seeking to apply the new techniques of genetic engineering to human diseases.
In 1978, a synthetic version of the human insulin gene was constructed and inserted into the bacterium Eschericia coli, in the laboratory of Herbert Boyer at the University of California at San Francisco. Insulin is a protein, and like all proteins, it consists of a chain of building blocks called amino acids, as pictured in the figure above. The order of amino acids in a protein is not random; rather, it is unique to that particular protein. When the sequence of amino acids is known, the corresponding sequence of DNA can be isolated (or in this case, chemically synthesized) and introduced into bacterial cells to make the human protein.
To accomplish this, the piece of foreign DNA is first inserted into a plasmid, a small circle of DNA which serves as a carrier. The new "recombinant" plasmid carrying the human gene is then reintroduced into another bacterial cell. Once inside the cell, the human gene on the plasmid can be read by the cell's protein-making machinery.
At the time, the approach that Boyer and his colleagues took in synthesizing a gene was unheard of. Today, however, this approach is more common, and other methods of directly or indirectly isolating human DNA are used more routinely. Recombinant human insulin was developed by Boyer's fledgling company, Genentech, in October of 1982, the first product of modern biotechnology.
Since that initial success, the application of biotechnology to human medicine continues to grow at a phenomenal rate.
