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A genetically modified organism, or GMO, is an organism that has had its DNA altered or modified in some way through genetic engineering.
In most cases, GMOs have been altered with DNA from another organism, be it a bacterium, plant, virus or animal; these organisms are sometimes referred to as "transgenic" organisms. A gene from a spider that helps the arachnid produce silk, for example, could be inserted into the DNA of an ordinary goat.
That may sound far-fetched, but that exact process was used to breed goats that produce silk proteins in their goat milk. The milk is then harvested and the silk protein is isolated to make a lightweight, ultra-strong silk with a wide range of industrial and medical uses.
Genetically modified food
The range of GMOs can boggle the mind. Geneticists have bred GMO pigs that glow in the dark by inserting into their DNA a gene for bioluminescence from a jellyfish. Tomatoes have been developed that resist frost and freezing temperatures with antifreeze genes from a cold-water fish, the winter flounder (Pseudopleuronectes americanus). As with many early GMO experiments, that one was less effective than hoped and was never brought to market.
By far the biggest use of GMO technology has been in large-scale agricultural crops: At least 90 percent of the soy, cotton, canola, corn and sugar beets sold in the United States have been genetically engineered.
The GMO crops that are widely used have, for the most part, been genetically engineered to control pests in one of two ways: They either produce a pesticide within their tissues, or they are resistant to a pesticide like Roundup (manufactured by Monsanto Corp.).
One widely used method of incorporating insect resistance into plants is through the gene for toxin production found in the bacterium Bacillus thuringiensis (Bt), according to the World Health Organization. GMO crops that are modified with the Bt gene have a proven resistance to insect pests, thus reducing the need for wide-scale spraying of synthetic pesticides.
In addition to pest resistance, GMO crops can be engineered for disease resistance, drought tolerance, added nutrients, hot or cold temperature resistance and other beneficial traits. These genetic enhancements, however, aren't universally welcomed, and there's been widespread resistance to the development and marketing of GMO crops and other organisms.
How safe are GMOs?
It depends on whom you ask. A large number of anti-GMO activists — who refer to GMO crops as "Frankenfoods" — believe GMOs can cause environmental damage and health problems for consumers.
"Genetically modified foods have been linked to toxic and allergic reactions, sick, sterile and dead livestock, and damage to virtually every organ studied in lab animals," according to the Institute for Responsible Technology, a group of anti-GMO activists.
"Most developed nations do not consider GMOs to be safe," according to the Non-GMO Project. "In more than 60 countries around the world, including Australia, Japan and all of the countries in the European Union, there are significant restrictions or outright bans on the production and sale of GMOs."
However, many scientific organizations believe the fear-mongering that runs through discussions of GMO foods is more emotional than factual. "Indeed, the science is quite clear: crop improvement by the modern molecular techniques of biotechnology is safe," the American Association for the Advancement of Science (AAAS) said in a 2012 statement.
"The World Health Organization, the American Medical Association, the U.S. National Academy of Sciences, the British Royal Society, and every other respected organization that has examined the evidence has come to the same conclusion: Consuming foods containing ingredients derived from GM [genetically modified] crops is no riskier than consuming the same foods containing ingredients from crop plants modified by conventional plant improvement techniques," according to the AAAS.
"Since GM crops were first commercialized in 1996 … regulatory agencies in 59 countries have conducted extensive scientific reviews and affirmed the safety of GM crops with 2,497 approvals on 319 different GMO traits in 25 crops," according to a statement on the website for Monsanto, the world's largest manufacturer of GMOs. "The majority (1,129) of approvals on GM crops have been on the food safety of the product."
GMO labeling debated
These assurances, however, do little to appease opponents of GMO development — and there have been cases where GMOs have caused harm. Potatoes engineered with a lectin gene (for resistance to pests) were linked to stomach damage in rats that consumed the potatoes, according to a report from the University of California, Davis. And in 1989, 37 people died and about 1,500 were sickened after ingesting L-tryptophan (a nutritional supplement) that was manufactured by a strain of GMO bacteria.
In both of these cases, however, it could not be determined that the GMO food itself was the cause of the problems: The L-tryptophan, for example, may have been contaminated with an impurity that arose from the manufacturing process, not from the L-tryptophan.
The argument over the development and marketing of GMO foods has become a political hot potato in recent years. In 2012, voters in California were asked if food made from GMOs should be labeled as such. The initiative was defeated — but only after GMO proponents like Monsanto, General Mills, Pepsico, DuPont, Hershey, Cargill, Kellogg, Hormel, Kraft, Mars, Goya, Ocean Spray, Nestle and other industrial food marketers spent millions on advertising to convince voters to vote against the measure.
Opponents in several states and countries continue to push for GMO labels on foods — if not outright bans on GMO foods — but industry and science insists the foods are safe, labels aren't needed and they'll just confuse consumers. Only one thing is certain: The battle for and against GMO crops, and the foods containing them, isn't likely to end soon.