Detection of Genetically Modified (Transgenic) Foods As the power for weaving the fabric of life is newly placed in the trembling hands of humanity it is crucial to insure the intentions of researchers and developers do not unleash Pandora’s box upon the world. The development of new methods to detect the presence and possible spread of transgenic foods is vital in monitoring the safety of genetically modified foods. The development of new tools to quickly identify detrimental genes will also prove invaluable as mankind attempts to tame the dangers already present in our own gene pool. Food products have been altered in many ways to improve product yields and nutritional values. The protein product of the gene Bt in the bacteria Bacillus thuringiensis has been found to paralyze the digestive systems of many species of insects and has been built into the plants themselves. If certain pests eat these plants they will soon die of starvation no matter how much they eat. Plants have been created which not only have built in insecticides, but are also resistant to herbicides. Roundup is extremely effective in killing most plants by inhibiting 3-enolpyruvylshikimate 5-phosphate (EPSP) synthetase in the Aromatic Amino Acid Pathway. The herbicide doesn’t spread far from where it is sprayed, which is beneficial for wildlife and water supplies surrounding the farmlands. Roundup wasn’t previously sprayed on crops: It would kill all of them along with the weeds. Fortunately, genes of other bacteria possess an immunity to Roundup due to their altered EPSP synthetase. The genes for this altered pathway have been inserted into plants making them immune to Roundup. After genetically modifying the crops, Roundup can be sprayed directly on farmlands, eliminating all weeds without endangering the harvest. Beef and milk products are even being made more nutritious with insertion of new enzymes into the animal genomes. There is a large amount of public resistance to the use of these genetically modified foods. Protestors of these "Frankenfoods" have slashed farms in Europe. Most supermarkets in Europe either won’t sell transgenic food or are required to label them. The rejection of these products in the US has been nowhere near the severity seen in Europe, but organizations such as Friends of the Earth and the Sierra Club are attempting to rally the public to the same outrage. There are many objections to the foods. People fear the government has not done enough tests on the food to insure their safety. Just as bacteria are able to acquire resistance to antibiotics by transferring plasmids, there is a concern about the transference of these super-genes to weeds and bacteria. An unconfirmed rumor about transgenic potato genes being spread to laboratory rats caused the production of those potatoes to be halted until further tests could be done. Some transgenic plants have a resistance to ampicillin. It is feared this resistance could enter the genome of infectious bacteria and provide them resistance to the drug. If the weeds were somehow able to obtain genes through the pollen of engineered plants, they would become very difficult to kill. People even doubt the effectiveness of the insect-proof plants over time and believe meddling with nature will only produce a conduit through which our present means of defending crops will be lost, or worse, intercepted by "the enemy." The need to detect these transgenic foods arises from several areas. Detection of the transgenic vectors is necessary to determine if the engineered traits are indeed being passed to other species. Detection would also be used to single out transgenically produced products to the purchasers of the goods. This identification would help insure the modified products are being properly labeled for sale where required. Imported transgenic crops can be easily identified and regulated as well. A couple methods of detecting transgenic products are commonly used. The first utilizes immunoassays. Immunoassays are constructed to find the presence of a specific molecule, in most cases a protein. Assays to detect transgenic proteins must be made with an idea of what types of proteins are unique to genetically modified organisms (GMO’s). First, these altered GMO proteins are injected into a lab animal. Then the animal’s immune system forms antibodies to the foreign protein, just as your body produces antibodies to a foreign invading pathogen such as a cold virus. To isolate the particular antibodies, the spleen cells are removed from the animal. The spleen cells are chosen because that is the source of a large number of antibody-producing cells, called B cells. These B cells are then fused with cancerous myeloma cells. This type of fusion is called hybridization and produces a cell containing genetic material from both cells. The result is a cell possessing both the immortality of a cancerous cell and the antibody production of a B cell. The hybridized cells are screened to isolate the hybridoma clone that produces an antibody of single specificity for the transgenic protein. These cells can be used to produce large amounts of the antibodies that will bind specifically to the transgenic protein. Because the hybridized cells only produce one type of antibodies, they are called monoclonal antibodies. The immunoassay to detect the transgenic antibody is formed by bonding these antibodies to a polymer support. The antibody-lined polymer support is washed to remove unattached antibodies and exposed to the suspected transgenic proteins. The support is then blocked so no other proteins can bind to it. A ground-up sample of the food in question is added to the assay. The antibodies on the solid support will retain any transgenic proteins matching the antigen to which they were designed to bind. After this step, another wash will remove any unbound proteins, as these were not recognized by the affixed monoclonal antibodies. A second antibody is then introduced that also recognizes the transgenic antigen and bind to it. This forms a "sandwich" of the first and second antibodies around the antigen. Another wash is done to remove any unbound secondary antibody. This secondary antibody is significant because it is tagged with either a fluorescent label or an enzyme that will react to certain dyes and their color. Either way, any fluorescence or color change (upon addition of the color-producing dye) will indicate the presence of transgenic material in the foods tested. If no color is generated, then the food is unmodified. A more accurate and increasingly popular method is the use of polymerase chain reactions (PCR). PCR is a method for amplifying specific segments of DNA from a large pool of genetic material. Primers are added to the PCR reaction that will recognize and bind to sequences found only in the transgenic genes. In this manner, the PCR reaction will amplify transgenic DNA, and indicate its presence when an investigator visualizes any DNA that was amplified by gel electrophoresis. PCR also provides greater sensitivity. The chance of the primer attaching to the wrong site is extremely low whereas similar proteins may attach to the same antibody in some cases. The possibility for amplification of a signal is much greater with PCR since the process amplifies its results every time it is allowed to cycle. Immunoassays are limited in the number of tags that can be attached to a single antigen. There is also the risk that the transgenic protein is not being synthesized in large amounts or at all during the collection of the immunoassay samples. PCR, in interacting directly with the DNA, bypasses these risks. Genetically modified foods offer the world new possibilities beyond more nutritious food and better crop yields. Plans are currently underway to put vaccines in the plants of underdeveloped nations. Although the concerns of the critics of transgenic food are viable the probability of genetic transfer between higher eukaryotic organisms is incredibly low, there is a much greater chance of natural evolution enabling unwanted plants to develop resistance. Nonetheless, the technology used to detect genetically modified organisms will come of great use to help insure the genes constructed to benefit society are not to its detriment. The development of new tools to quickly identify detrimental genes will also prove invaluable as mankind attempts to tame the dangers already present in our own gene pool. Not only does the detection of transgenic genes keep science in check for today, but also may help to develop a means of quickly identifying any dangerous genes, such as those leading to Parkinson’s and Alzheimer’s disease as we approach a future where they will be correctable. GM Foods and Their Detection Web Site Links Genetic ID: Identifies transgenic products Negative views on GMO. Intekom: US Chemical Giant Monsanto Wields Control Copyright © 1999, Harcourt College Publishers, A Harcourt Higher Learning Company. All rights reserved. Use of this site indicates acceptance of the Terms and Conditions of Use. For problems or suggestions concerning this service, please contact Chemistry Webmaster.