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Genetically modified organisms

The availability of genetically altered foods continues to be a hotly debated issue with powerful lobbies on both sides. Corn that resists attacks by insects, canola that is tolerant of herbicides, and cheese that can be made without using animal rennet have been some of the advances introduced by genetic modification, but some people worry that possible long-term effects may not have been adequately assessed.

For centuries, food growers have tampered with plant and animal genetics by crossbreeding in order to bring out desirable traits while suppressing less desirable ones. The refinement of such techniques has enabled farmers to produce increasingly abundant crops.

In recent years, food biotechnology has added a new dimension, thanks to genetic modification. Genetically modified (GM) foods or genetically modified organisms (GMOs) are terms that refer to a change in the code or organization of the genetic material of an organism. One method to achieve this change is "genetic engineering" the practice of moving one gene or group o genes from one organism to another.

The production of GMOs is regulated in the United States and Canada. To date, each country has approved at least 40 plant varieties derived by genetic modification. Soybeans, corn, and canola are the most widely produced GM crops and furnish a number of ingredients that are used in highly processed foods. In fact, about 70 percent of processed foods contain at least some GM ingredients.

Improving on nature

Genetic engineering enables research botanists to add desirable hereditary traits to almost any plant. Possibilities include producing more nutritious foods; for example, corn with increased high-quality protein, or a type of rapeseed that synthesizes more of the unsaturated fatty acids of canola oil.

Agricultural scientists are also trying to alter plants to make them more productive or more able to withstand adverse growing conditions, such as drought. this type of genetic engineering has tremendous potential in overcoming world food shortages; conceivably, arid desert areas may one day produce drought-resistant grains.

Another approach involves engineering plants to be resistant to disease, herbicides, and pests. One modification alters a plant's taste to make it less attractive to insects, allowing farmers to reduce pesticide use.

Another is aimed at developing a plant resistant to new kinds of herbicides that do not harm the crops and beneficial insects.

Cheese producers have also benefited from genetic modification. The classic way to make cheese involves using rennet extracted from calf stomachs to curdle milk. But chymosin, the major enzyme in rennet can also be produced through genetic engineering. The bit of DNA, the gene, that gives the instructions for the formation of chymosin has been isolated from calf cells and copied, or "cloned." Inserting this gene into the genetic machinery of certain bacteria (Escherichia coli), yeasts (Kluyveromyces lactis), or fungi (Aspergillus niger) causes them to dutifully churn out pure chymosin. Approved in 1990 by the Food and Drug Administration in the United States, chymosin became the first product of genetic engineering in our food supply. It is 100 percent identical to that found in calf stomach, but because it does not come from animals, it is acceptable to consumers who do not want meat products in their cheese.

Extraordinary precautions were taken before chymosin, made by recombinant DNA technology, was marketed. Regulators ensured that no toxins of any kind had been introduced and that no live recombinant organisms were present. Cheese made with it is completely indistinguishable from that produced with animal rennet. In any case, chymosin itself is degraded ruing cheese making and none is left in the finished product. today, In North America, more than 80 percent of cheese is made using chymosin.

The downsize

Despite the benefits of genetic modification, some people are concerned that this type of manipulation may create adverse consequences.

Gene transfer to nontarget species. For instance, scientists will often incorporate an antibiotic-resistant gene (or tracer) into the genetic material that is being introduced into a plant. If the modified cell is able to survive antibiotic treatment, it means that it has become resistant to that antibiotic and has probably taken on other characteristics carried in the newly added genetic material. So far, evidence that antibiotic-resistant tracers can be transferred to a nontarget species such as a disease-causing microorganism is sketchy, but theoretically, it could happen.

Reduced effectiveness of pesticides and herbicides. There is some concern that insects will become resistant to the pesticides produced by crops that have been genetically modified to produce their own pesticides, or that the herbicide resistance of a GM crop will be transferred to a weed Another concern is that these crops may harm beneficial insects along with the intended crop-damaging pests.

Unintended harm to the organism or other organisms. Comparatively, animals subjected to genetic engineering do not fare as well as plants. For example, sheep injected with genetically engineered hormones to increase wool growth become more vulnerable to the heat. Pigs and chickens treated with special growth hormones develop painful bone and joint problems.

Also, there are ethical issues involved in tampering with animal genes.

Allergic reactions. Concern has been raised that allergens may be transferred through genetic modification. This is unlikely to occur because the structures of proteins introduced by genetic modification are compared with extensive data bases of the structures of known allergens.

It's a question of benefits versus risks

The potential benefits of genetic modification are numerous. Sweet potato is an important crop in Africa but is very susceptible to feathery mottle virus. Inserting a set of genes from chrysanthemums that code for naturally insecticidal compounds called pyrethrins has the potential of creasing yields dramatically. the use of pesticides on cotton has already been dramatically reduced by incorporating a gene that protects it from insects. While there are environmental concerns about pollen drift and crossbreeding with non-GM plants, there has not been a single adverse health effect.

     
     

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