Genetic Engineering: Future Foods : Part 2

by Food and Drug Administration (FDA)

(Page 2 of 3)

A New Twist on an Old Idea

For the last 12 years, genetic engineering has inhabited agricultural research laboratories and only now is making its initial appearance in food stores.

In May 1994, the agency gave the OK to a whole food product, a slow-ripening tomato. The tomato's developer, Calgene, Inc., seeking to build public understanding and confidence in the new product, decided to ask FDA to conduct a comprehensive safety review for the new tomato, called the Flavr Savr. Since then, FDA has not found it necessary to conduct comprehensive scientific reviews of bioengineered foods but, consistent with the 1992 policy, developers have been following a consultation process. To date, developers have completed this process for over 30 products that include three tomatoes with modified ripening or softening properties; herbicide tolerant crops (glyphosate-tolerant soybean, cotton, corn and canola; glufosinate-tolerant canola, bromoxynil-tolerant cotton); pest resistant crops (virus-resistant squash and papaya, insect-protected corn, potato and cotton) and vegetable oils with modified fatty acid profiles (laurate canola and high oleic soybean oil).

FDA has also affirmed as GRAS (generally recognized as safe) other genetically engineered products for use in food production including chymosin, a milk-clotting agent used to make cheese, and recombinant bovine somatotropin (rbST), a growth hormone that boosts a cow's milk yield.

Though the notion of tinkering with a plant's traits is thought of as something radically new by some people, scientists have been doing it for many years in cruder, less predictable ways. For example, farmers have a long tradition of breeding desired qualities into crops. But this process took many plant generations. Researchers now can isolate a known trait from any living species — plant, animal or microbe — and incorporate it into another species. These traits are contained in genes — segments of the DNA molecules found in all living cells. The process of recombining genes bearing a chosen trait into the DNA molecules of a new host is called "recombinant DNA technology."

In ancient times, farmers practiced a less refined version of genetic manipulation by saving seeds from crops that proved the hardiest and most resistant to disease. By selecting which plants they would breed, these farmers "engineered" new combinations of genes, ones that would produce superior plant stock. By the 1500s, farmers were improving plants by crossing, for example, a productive crop with a wild relative resistant to disease or pests. The result was a hybrid, a new species that embodied desirable traits from both "parents."

In the mid-1800s, Austrian monk Gregor Mendel revolutionized genetic science by employing precise pollination methods and statistical analysis. Mendel's pioneering methods allowed scientists later to determine how specific traits could be inherited into subsequent generations and to "coax" plants to swap traits they wouldn't readily exchange in nature.

Advantages and Challenges

Genetic engineering gives today's researchers considerable advantages in plant breeding programs, but it also poses new challenges. One important benefit is predictability, says Maryanski. Scientists, he says, now can identify the specific gene for a given trait, make a copy (clone) of that gene for insertion into a plant, and be certain that only the new gene is added to the plant. This eliminates the "backcrossing" traditional plant breeders must do to eliminate extraneous undesired genes that are frequently introduced when using cross-hybridization.

"The limitation," says Maryanski, "is that the scientist must be able to identify the gene for a desired trait. For example, if you wanted to improve the yield of a food crop, that trait may be encoded by several genes. Such an improvement would be very difficult to achieve at this stage of the technology." Thus, he adds, crop improvement through recombinant DNA techniques is restricted to traits for which scientists can identify the appropriate genes.

Another advantage of new methods is a significant acceleration of the development timetable. "Conventional breeders may find a plant with the traits they want," says Maryanski, "but it will likely have many other unwanted genes that come along with the desired genes. So they spend literally years trying to remove the undesirable traits and still maintain those they wanted in the first place." Traditional techniques typically take 12 or more years to create a new strain, compared to about five years using recombinant DNA procedures. Despite the speed advantage, the newer methods are "not just a quick afternoon in the laboratory," Maryanski says. "There are a lot of tricks used that actually get the new plant cells to grow." Plant breeders do not use recombinant DNA techniques exclusively. Instead, they use a combination of new and traditional methods to provide a plant with quality, yield, weather and pest resistance, and other desirable traits. For example, "the gene insertion doesn't always 'take' — that is, the gene might not stay there," Maryanski says. So recombinant DNA researchers still have to pass plants through several generations using conventional methods to ensure the desired trait truly has been incorporated, a process called stabilization.

Power Concerns Some

Another difference with recombinant DNA, which can be a benefit but which concerns some, is the "power" of genetic engineering — the ability to transfer genes from a wide variety of species. Because the chemical makeup of DNA is similar in all living things, desirable genes from any organism can be inserted into a plant species. This provides the developer with a much larger selection of valuable traits. For example, one developer experimented with using a gene isolated from a fish, the winter flounder, to impart freeze resistance into a variety of tomato. Such research prompted concerns among some consumers, especially vegetarians and members of certain religious groups. They wondered if the process of inserting an animal gene into a plant somehow could create a vegetable that is part animal and should be labeled.

Maryanski says most scientists don't believe this is possible because only a copy but no original material from the animal is used. "Also," he says, "one can't really confer animal-like characteristics on a plant because only one gene for a very specific trait transferred." He acknowledges, however, that though no plant products using animal-derived genes are planned for marketing in the near future, the animal gene issue is a weighty one that deserves "considerable discussion" within the scientific community and the general public.

About the Author

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FDA is A United States government body that oversees medical devices, including contact lenses, intraocular lenses, excimer lasers and eyedrops. In the US, these products must be approved by the FDA before they can be marketed.