Manipulation of genetic material is not new. Scientists have been selecting for desired plant and animal characteristics for centuries. These selective breeding efforts have helped make the United States a world leader in the production of food, feed, and fiber.

In the past, when breeding for improved genetic characteristics, the genetic pool was limited to genes within the same species or between very closely related species. For example, wheat could not be crossed with corn. This restriction limited access to some potentially useful genetic characteristics and novel combinations.

New biotechnology techniques have removed this restriction. It is now possible to take a single gene from one organism and incorporate it into a totally unrelated species. The resulting plant, animal, or microbe looks like the original organism, but displays the desired genetic trait of the donor organism. Plant and animal products resulting from these new techniques are helping reduce production costs for farmers, protecting the environment, and improving the nutritional quality of our food sources.

DNA, Genes, and Genetic Engineering

Deoxyribonucleic acid (DNA) carries the genetic information code within the cell. DNA is present in the same form and is composed of the same chemical components in every cell of every living thing. Human DNA is composed of the same substances as the DNA in trees, grass, birds, horses, and bacteria.

Cells contain long strands of DNA, which are called chromosomes. Every human cell has 46 chromosomes and all the information that is needed to make us unique human beings is contained in these chromosomes.

DNA itself is made up of a series of compounds called nucleic acids. The arrangement of these nucleic acids—the DNA sequence—acts like a set of blueprints. The sequence tells the organism what to make, when to make it, and where to make it. Each person is unique because the nucleic acids of his or her DNA are arranged differently.

Simple traits come from complex genes.
This illustration shows how the gene that determines flower color is created.

A gene is a segment of DNA that directs or codes for the production of a protein; proteins determine particular traits. Take, for example, the gene for flower color. The arrangement of the nucleic acid compounds on a chromosome in one plant tells the flower cells to produce certain proteins that make the flower blue. On another plant, the nucleic acid compounds are arranged differently, instructing the plant to make pink flowers. Eye color in humans is similar. One person's genes produce proteins that make eyes brown, while another person's genes produce proteins that make eyes blue.

Other traits—like height and size in humans, or a plant's ability to withstand freezing temperatures—are more complex. Many genes interact to produce the right proteins, which generate these traits.

Some genes have control regions on the chromosome. These region are like a light switch or a thermostat. They turn the gene on or off, or regulate the amount of protein produced. While cells carry identical DNA codes, different cells have different functions. For example, the cells of your fingertips do not need to make the proteins that color your eyes. The gene for eye color protein is turned on in your eyes and turned off in your fingertips. Likewise, the gene that makes a flower pink is not needed in the root, so it is turned off in the root cells and turned on in the cells of the flower.

New biotechnology techniques allow researchers to take certain genes from a source organism and put those genes into another plant or animal. Similar techniques can be used to regulate the amount of protein produced by a gene. These techniques are called genetic engineering.

Genetic engineering can result in a new flower color, or it can add resistance to
harmful insects in corn, as seen below. Enzymes are used to "cut" and "insert" the
desired gene. When the Bt gene is incorporated into corn and cotton, the new plants
are resistant to many harmful insects so farmers can reduce pesticides.

The use of a gene from a commonly occurring soil bacteria called Bacillus thuringiensis is a good example of successful genetic engineering in agriculture. Bacillus thuringiensis has a gene known as the Bt gene, which produces a protein harmless except to caterpillars. The bacteria and its protein present no risk to humans, animals, or beneficial insects, but it turns toxic in the digestive tract of caterpillars.

Scientists have taken the Bt gene from the bacteria and incorporated it into the chromosomes of cotton and corn, creating what is known as transgenic or transformed plants. Transgenic cotton and corn produce the Bt protein. Now, caterpillars die when they feed on the transformed cotton or corn, and insecticide sprays to control caterpillars are not needed.

Scientists have discovered a gene that makes corn resistant to certain damaging insects.

Carolina cotton producers have reduced pesticide sprays and lowered production costs by utilizing genetically engineered cotton varieties.

Genes that can make crops resistant to specific herbicides have been identified. Of particular interest are the genes that make plants resistant to Roundup, an effective and environmentally friendly herbicide. By incorporating the herbicide-resistant genes into the DNA of the crop, farmers can keep weeds down with an environmentally safe herbicide without injuring the crop. Research is currently underway to incorporate resistance to other effective and safe herbicides.

Thanks to genetic engineering, North Carolina
soybeans can now be sprayed with Roundup, making
weed control easier, less expensive, and safer for the environment.

Genetic engineering can also be used to turn genes on or off. The Flavr-Savr tomato, one of the first genetically engineered foods to hit the market, is a good example. The enzyme naturally produced by the tomato that generates an off flavor and mushy texture was turned off. The result is a vine-ripened tomato that can be shipped with minimal bruising and spoilage.

A new use for genetic engineering is regulating the production of desired proteins with the idea of "mining" these proteins. For example, genetically engineered tobacco plants may be used to produce large quantities of lysozyme, an enzyme used in many detergents. Tobacco already has a small amount of naturally occurring lysozymes. The genetic control region that regulates production of lysozyme can be turned up, much like we turn up the thermostat at home when we want more heat. Genetically engineered tobacco can be harvested and the lysozyme mined from the leaves. Similar techniques are being used to mine pharmaceutical chemicals.
Biotechnology and Animals
Animals raised for food can be genetically engineered in ways similar to plants. This gives consumers more abundant, healthier food at a lower price. Leaner meat and higher yields of milk are real possibilities for the future.

Bacteria has been genetically engineered to produce bovine somatotrophic (BST), a natural milk-stimulating protein found in cows. Cows injected with BST produce more milk. The milk produced by this method is safe, wholesome, genetically identical to milk produced without the additional BST, and has been endorsed by the Food and Drug Administration. Other types of somatotrophics administered during the growth phase of animals will result in leaner meat and faster growth.

Advances have also been made in producing transgenic livestock, which would serve as models of human diseases. Researchers could then use these transgenic livestock to design and test human diseases. Experiments are also underway to produce transgenic pigs that could serve as organ donors for humans. Down home on the farm, pigs could soon be raised for lifesaving biomedical research and treatment, as well as for food to sustain us.

Are Geneticially Engineered Products Safe?

One of the most frequently asked questions about genetically engineered crops and animals relates to food safety. Are these food and feed products safe to eat?

Genetically engineered foods can take a variety of forms. It can be the food itself, as the Flavr-Savr tomato; foods containing genetically modified organisms, as in fermented bread or cheese; or ingredients (enzymes, gums, flavors) produced through biotechnology.

In each case, the products of the technology are evaluated for safety before they are released to the consumer. Because recombinant DNA technology allows precise genetic changes to be made, the resulting plants, animals, or microorganisms are less likely to carry genetic defects or abnormalities. Most food scientists who work with biotechnology consider genetic engineering to be a much safer and more controlled approach to improving, expanding, and protecting our foods.

Genetic techniques to modify animals, plants, and microorganisms will lead to tremendous gains in the quality and quantity of our food supply. In the United States, the products of these technologies will be closely evaluated by university and industry scientists, regulatory agencies, and consumer protection groups. This will assure their environmental compatibility and safety before release. Advances in scientific fields such as toxicology and immunology put science in a better position to evaluate and recognize potential hazards and assure product safety of any new foods derived from biotechnology. As with any food or food process, safety remains paramount. It is seriously considered before any product is placed into the food production or distribution chain.

Have You Eaten Cheddar Cheese Lately?
One of the most successful applications of recombinant DNA technology for foods is the production of chymosin, an enzyme used in cheese making. Chymosin, when added to milk, causes the curd to form.

Chymosin, which was available only from the stomach of calves, was in limited supply due to a reduction in the veal industry and expansion of the cheese industry.

Then the gene for chymosin production was incorporated into the DNA of both bacteria and yeasts. Pure chymosin can now be made. The enzyme is identical to that produced in the calf and the process itself adds no contaminants. The FDA evaluated the safety of the process and the product itself in 1990 and ruled that the enzyme preparation was safe for human consumption.

Since then, chymosin produced by recombinant DNA organisms has been widely used in making Cheddar cheese. Most Americans who have had a slice of Cheddar cheese since 1990 have eaten a product improved by biotechnology.

In Summary

Genetic engineering is a tool that has greatly affected agriculture and will continue to bring dramatic advances in crop and animal production. Biotechnology has improved the quality of food, feed, and fiber, and it often lowers production costs and provides for a safer farm environment. Many possibilities await. Scientists are exploring ways to incorporate resistance to disease, nematodes, and other insects into plants. Animal scientists are evaluating possible ways to increase animal growth and to "mine" proteins from milk. Research in the use of bacteria and viruses to produce enzymes and medicines is already under way.

Genetic engineering has a lot to offer. We have only begun to see the products and possibilities. The North Carolina Cooperative Extension Service has several publications and videotapes on the subject. Contact your county center for more information.