Above: Teosinte (top), Maize-teosinte hybrid, and Maize (John Doebley)
In recent years, GMOs (genetically modified organisms) have been the subject of protests, advertising campaigns, and referendums. But what is a GMO? And what is the difference between genetically engineered (GE) and genetically modified (GM) plants? This article uses different varieties of corn (maize) illustrate the difference between GM and GE, since all modern varieties of corn are GM crops, but not necessarily GE.
Did You Know? Mutagenesis is the process of changing an organism's genetic information. It can occur naturally or be the result of chemical, biological, or physical treatments.In fact, there is no unanimous agreement on the meaning of these terms. However, the following definitions reflect the general consensus:
“Genetically modified” is a broad term referring to any organism whose genetic makeup is changed by humans. These changes can be accomplished by a variety of means, from biotechnology to less “high-tech” methods such as selective breeding and mutagenesis.
“Genetically engineered” refers to a specific type of genetic modification, where an organism's DNA is altered using biotechnology. This usually involves adding a gene from a different organism. The new gene might provide pest or herbicide resistance, or additional nutritional benefits.
Therefore, all GE organisms are also GM. But not all GM organisms are GE (GE is a subset of GM).
Did You Know? The gene making GE corn resistant to the corn borer insect originates from a type of bacteria called Bacillus thuringiensis. Spores of these bacteria contain a “Bt toxin” that kills lepidopteran insects (moths and butterflies).The corn plant, as we recognize it today, was created by farmers in what is now southern Mexico approximately 10,000 years ago. That was quite a while before the age of genetic engineering! One technique these farmers had at their disposal was cross-breeding: breeding two plants with different characteristics in the hopes of creating a new species that retained the desirable traits of both “parents.” A second technique was artificial selection: keeping only seeds from the best plants for replanting next season.
Armed only with these two simple methods, ancient farmers turned a wild grass called teosinte into a crop resembling modern corn. If you enjoy fresh corn on the cob, you should be glad they did. Compared to corn’s soft and plentiful kernels (500 or more per cob), teosinte has tiny ears with only five to 12 kernels. And each kernel is surrounded by a rock-hard covering!
|The first commercially-available GE crop, Bt corn, was engineered to resist the European corn borer, Ostrinia nubilalis, pictured above (USDA) |
Many modern varieties of corn are not only GM, but also GE. Certain varieties have been engineered to express traits such as herbicide tolerance, allowing farmers to kill the weeds with herbicides without killing the corn, and pest resistance, keeping the corn borer at bay. Other varieties of corn now exhibit drought tolerance, which is expressed using a more recently discovered transgene (inserted gene). In fact, farmers can now buy corn seed with stacked traits (genes from more than one other organism), providing a combination of desired traits that improve crop productivity.
Although the terms GE and GM are often used interchangeably, the distinction is extremely important to regulators and those who oppose genetic engineering. Crop-breeding techniques for creating GM plants have been practiced for thousands of years. For example, since they have been modified by humans to be different from teosinte, all varieties of corn are GM. Those developed by the ancient Mexican farmers, as well as several modern varieties that are marketed as “non-GMO,” have not been altered by biotechnology, so they are GM but not GE. Only those modern varieties that have been manipulated by biotechnology are considered GE. Methods for creating GE crops were only developed in the 1970s. The first GE crop, Bt corn, was field tested in the mid-1980s and became commercially available in the mid-1990s.
As a relatively new technology, there is ongoing controversy over whether GE foods are safe for humans and the environment. GE crops are thoroughly reviewed and regulated before being approved for use as human food or animal feed. Crop breeding companies must provide regulators with detailed, scientifically-valid information, including reports on toxicology, levels of nutritional components, allergenicity, and potential effects on wild relatives and other species. Ultimately, it is difficult to predict exactly how GE crops like Bt corn will affect humans and the environment in the long run. While some argue that genetic engineering is not only safe but also a boon for modern agriculture, others believe it’s safer to avoid GE foods altogether.
Find out more about crop breeding techniques and Genetic Engineering by visiting the CurioCity Biotechnology Theme Page and the Agriculture and Biotechnology section of this website.
The Evolution of Corn (Genetic Science Learning Centre, University of Utah)
How Did Corn Evolve? (Moment of Science, Indiana Public Library)
Genetically Modified Foods: Harmful or Helpful? (Proquest Discovery Guides)
Food and Drug Regulations (Department of Justice, Government of Canada)
Glossary of Terms (AgBiosafety)