Genetic engineering is a discipline represented by the ability to isolate, modify the expression of, or transfer genetic material. Genetic engineering was born in 1973 when Stanley Cohen and Herbert Boyer reported the successful transfer of reptile DNA into bacteria. Practical applications quickly followed, and in 1980 Genentech became the first publicly traded genetic engineering company. Genentech's main product was human insulin produced in bacteria. It was marketed for diabetic patients who had developed allergies to the pig or sheep insulin used to treat diabetes. The enthusiastic response from investors led to many new genetic engineering companies. Many of the newest of their products are produced in genetically engineered animals. This practice is called pharming.
Insulin was just the first of many genetically engineered products. In 1995 there were over 100 genetically engineered therapeutic products approved by the U.S. Food and Drug Administration (FDA) or in clinical trials. They ranged from hormones like insulin and human growth hormone to vaccines, and included many products created to treat serious diseases such as muscular dystrophy, multiple sclerosis, and cancer. Genetic engineering has allowed scientists to explore genetic material in detail. In 2001 the preliminary report of the Human Genome Project was released, containing the nucleotide sequence of nearly all of the human genome (International Human Genome Sequencing Consortium 2001, pp. 860–921; Venter et al. 2001, pp. 1304–1351). A better understanding of human genetic makeup will allow scientists to understand both healthy cells and diseases better. Scientists are predicting that in a few years a patient will receive a DNA scan that will allow a doctor to prescribe medicines that match that patient's genetic makeup. These genetically tailored medicines are expected to be more effective and to have fewer side effects than their predecessors. A new scan technique called "DNA microarray" or "gene chip" is now available. With this technique a scientist or doctor can scan the identity of all the genes that a given tissue or cell is using at any time. This tool will be very powerful in helping to unravel the complex interactions of genes in diseases like cancer. It has already helped to identify the ways in which chemotherapy drugs interact, so that new more effective drug combinations may be developed. The same tool will help scientists to investigate cell growth and development. One important question that can now be asked is: Which genes are turned off or on as a cell ages?
One of the most exciting branches of therapeutic genetic engineering is human gene therapy. A single defective gene is often the cause of a disease, for example as with cystic fibrosis or sickle cell anemia. Gene therapy would allow doctors to transfer the healthy gene to the patient, and possibly allow replacement or removal of the harmful gene. For the first time doctors could cure genetic defects instead of being able only to treat the symptoms the defects cause. Trials of human gene therapy began in 1994 with some success (Anderson 1995, pp. 124–128), but much remains to be done before gene therapy can be used routinely. In addition, there are important ethical questions having to do with which genes will be identified as defective and which gene replacements will be allowed.
Agriculture is another area in which genetic engineering has become increasingly important. Many genetically engineered products are used in veterinary medicine and to enhance livestock-related production. For example, Bovine Somatotropin is used to increase milk production in dairy cows. It is becoming more common to use genetically engineered crops. Two of the most common examples are genetically engineered corn and beans. A kind of corn called Bt corn is engineered to contain and put to use a gene from a strain of bacteria that produces a toxin . This toxin kills insects that attack the corn so that farmers can use less insecticide on the field. Many soybeans are engineered to withstand a particular herbicide. Farmers can apply the herbicide to kill weeds in a planted field without harming the soybeans. All of these innovations have been very successful, but have provoked some concerns about human exposure to the new products, as well as new ecological concerns about "escape" of these genes into the environment. In one case Bt corn that had not been approved for human consumption accidentally made its way into human food products, and in another case the effects of Bt corn pollen on monarch butterflies have been questioned, but no answer is yet forthcoming. Genetically modified animals used to produce nonfoodstuffs such as those produced in pharming, and as laboratory models, are becoming more common.
Anderson, W. French (1995). "Gene Therapy." Scientific American 273(3):124–128.
Berg, Paul, and Singer, Maxine (1992). Dealing with Genes: The Language of Heredity. Mill Valley, CA: University Science Books.
Biotechnology (1995). A pamphlet from the American Chemical Society Department of Government Relations and Science Policy. It can be ordered free online at http://www.acs.org .
Cohen, Stanley; Chang, A. C. Y.; Boyer, Herbert; et al. (1973). "Construction of Biologically Functional Bacterial Plasmids In Vitro." Proceedings of the National Academy of Sciences 70:3240–3244.
Friend, Stephen, and Stoughton, Roland (2002). "The Magic of Microarrays." Scientific American 286(2):44–53.
International Human Genome Sequencing Consortium (2001). "Initial Sequencing and Analysis of the Human Genome." Nature 409:860–921.
Maulik, Sunil, and Patel, Salil (1997). "Preface." In Molecular Biotechnology. New York: Wiley-Liss.
Scientific American (1997). "Making Gene Therapy Work." Scientific American 276(6):95–123.
Venter, J. Craig, et al. (2001). "The Sequencing of the Human Genome." Science 291: 1304–1351.
Human Genome Project. More information is available from http://www.nhgri.nih.gov/HGP/ .