sealPurdue News

July 2000

Understand GMO crops? Test yourself with this quiz

WEST LAFAYETTE, Ind. – Nearly half of American farms grow genetically modified crops such as Bt corn or glyphosate-resistant (Roundup-ready) soybeans. Peter Goldsbrough, a plant scientist and expert in genetically modified crops at Purdue University, has developed 10 questions to test your knowledge of genetically modified foods and agricultural biotechnology:

1. As a result of genetically modified crops, chemical use on farms has:

a. Gone up dramatically.
b. Gone down dramatically.
c. Gone up on some but no change on others.
d. Gone down on some crops but there is little or no change on others.
e. Not changed.

2. The first plant that was modified by genetic engineering was produced in a laboratory in:

a. 1954.
b. 1964.
c. 1974.
d. 1984.
e. 1994.

3. Will insects develop resistance to the toxins produced in Bt corn?

a. It is impossible for insects to develop resistance to Bt corn.
b. It is unlikely that insects will develop resistance to Bt corn.
c. Under certain conditions insects may develop resistance to Bt corn.
d. It is almost certain that insects will develop resistance to Bt corn.
e. Insects are already resistant to the toxins produced in Bt corn.

4. Does Bt corn or Bt cotton only kill specific pests that damage the crop?

a. The Bt toxin kills all insects.
b. The Bt toxin kills European corn borer and other flying insects.
c. The Bt toxin kills the European corn borer and its close relatives.
d. The Bt toxin only kills the insects for which it is targeted.
e. The Bt toxin repels but doesn't kill insects.

5. When did crops become resistant to herbicides?

a. Crops have always been resistant to some herbicides.
b. After the introduction of Bt corn in 1997.
c. After the introduction of Roundup-ready soybeans in 1996.
d. Crops are not resistant to herbicides.

6. Can genes escape from genetically modified crops and jump to other plants?

a. Yes, and often do.
b. Only to some crops, but those crops aren't genetically modified.
c. Only during rare climatic conditions.
d. No, genes cannot move from species to species without human intervention.

7. If we make plants that survive in regions where they normally wouldn't survive, such as very cold regions, could this cause unexpected ecological changes?

a. No, the crops are only suited for cultivated fields.
b. It is possible that a crop might invade the surrounding ecosystem.
c. It is certain that the crop would move from the fields into the surrounding ecosystem.

8. How long does it take to develop a new genetically modified crop?

a. Twenty years.
b. Ten years.
c. Five years.
d. One year.
e. Six months.

9. Can scientists predict with certainty where an inserted gene will go on a plant chromosome?

a. With modern genetic techniques, scientists can insert genes precisely.
b. Genes are inserted on the proper chromosome, but there is no control on where it goes on the chromosome.
c. Scientists have a general idea of where the gene will go and what it will do to the plant.
d. It's just a shot in the dark.

10. Can agricultural biotechnology reduce our dependence on petroleum?

a. Most of it.
b. Some of it.
c. No effect on petroleum use.


1. Answer: d. Chemical use has gone down on some crops but there is little or no change on others. "In some cases the use of genetically modified crops may reduce the use of pesticides, but people are still going to use herbicides to control weeds," Goldsbrough says. "But it can reduce the use of some pesticides that are more likely to damage the environment, and that is progress."

2. Answer: d. 1984. "However, genetic modification and selection of plants has been going on for about 10,000 years, since the start of agriculture," Goldsbrough says.

3. Answer: d. It is almost certain that insects will develop resistance to Bt corn. Insect resistance to Bt toxin has already been demonstrated in the laboratory and observed in the field, according to Goldsbrough. "Insects will eventually develop resistance to the Bt toxin," he says. "Farmers are required to plant refuges of conventional crops and take other measures to slow down the development of resistance in insects, but it will eventually happen. Nobody knows when that will happen – this is a big ecological experiment that's going on."

4. Answer: c. The Bt toxin kills the European corn borer and its close relatives. Scientists were not surprised to learn last summer that monarch butterflies would die if forced to eat the Bt toxin. The European corn borer is the larva of a moth, and the Bt toxin will kill only moth or butterfly larvae that eat it. However, monarch butterflies typically don't eat the corn plant. "The Bt toxins produced by Bt corn aren't species specific," Goldsbrough says. "But they are much more specific than flying over a field with an airplane and spraying a general insecticide. The notion that this is a silver bullet is wrong, but so is the idea that this is killing all insects such as the monarch butterfly. Genetically modified crops offer a number of advantages compared to spraying insecticides."

5. Answer: a. Crops have always been resistant to some herbicides. "If they weren't, then farmers couldn't use herbicides such as atrazine on corn or some of the common herbicides on soybeans," Goldsbrough says. "While there is something novel about the herbicide-resistant crops produced through biotechnology, there is also something that is very much the same as before. This is more of an evolution than a revolution."

6. Answer: a. Yes, and often do. If crops are able to breed with wild relatives, the new genes will be spread to those wild plants. For example, sorghum can breed with the common weeds johnson grass and shattercane, and canola can breed with wild mustard plants. "So if you made Roundup-ready sorghum you'd quickly end up with Roundup-ready shattercane," Goldsbrough says.

Scientists safeguard against this by not releasing genetically modified crops in areas where wild relatives are present. "There are no relatives of maize [corn] and soybeans in the United States where the crops are planted," Goldsbrough explains.

Scientists did develop a technology that would prevent this crossover by making the genetically modified crops sterile. However, the technology came under attack from environmental groups, which labeled it the "Terminator gene," and the technology never made it to market.

7. Answer: b. It is possible that a crop might invade the surrounding ecosystem. "I don't think that's a likely scenario, but it could happen," Goldsbrough says. "For example, if you make strawberries that can resist frosts, you may have made the plant more competitive under certain conditions, and it is possible that it could become an exotic weed like wild mustard. That's something that's difficult to predict."

8. Answer: b. Ten years. "At the moment it takes approximately 10 years to develop a new genetically modified crop," Goldsbrough says. "It takes several years to test these genes to see how they work. Then the crops are evaluated under different environments over several years, just as other crops are evaluated before they're released to the growers. It's a long, careful process. That doesn't mean it's foolproof, but it's a deliberate process." Goldsbrough says new advances in technology, such as genomics, may speed the process of discovering desirable genes, but bringing new genetically modified crops to market will still take several years.

9. Answer: d. It's a shot in the dark. In some cases, a literal shot. For the most part, genes are moved into plants in one of two ways: using bacteria as carriers, or using air guns that shoot the genetic material into the cells. Just a few years ago scientists used .22 caliber blank cartridges to shoot the genes into the cells, giving the technique the label "gene gun." Once the genetic material is in the cells, the plants incorporate the DNA into their own chromosomes. But because scientists have no control over where the genes might go in the plant cells, they must germinate, grow and test hundreds or thousands of plants to find the ones where the introduced genes work properly and produce the desired traits. "The current state-of-the-art technology is unpredictable. Where the genes end up is a random process and can have unanticipated effects," Goldsbrough says. "But the plants that don't have the appropriate characteristics are discarded."

10. Answer: b. Some of it. "Plants harvest the energy in sunlight, the ultimate renewable resource, and plants are being developed that will produce plastics, fuels and other high value products. This has the potential to reduce our consumption of petroleum-based products. Biotechnology may allow us to reduce our reliance on fossil-based fuels," Goldsbrough says.

Source: Peter Goldsbrough, (765) 494-1334;

Writer: Steve Tally, (765) 494-9809;

Purdue News Service: (765) 494-2096;

Related Web sites:
Biotechnology time line
International Food Information Council Foundation survey on consumer views on biotechnology

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