Frequently Asked Questions about Genetically Modified Crops

Revised on March 27, 2014

Frequently Asked Questions Frequently Asked Questions about Genetically Modified Crops

By Annet Namuddu

  1. What is a genetically modified (GM) crop?
    A genetically modified crop is a plant to which one or more genes coding for desirable traits have been added through genetic engineering.
  2. What is genetic engineering/modification?

    Genetic engineering involves transfer of desired genes from one species to another using recombinant DNA technology.

  3. What are genes?

    Genes are basic units of hereditary information. A gene is a segment of DNA that expresses a particular trait or contributes to a particular function. Genes determine function or affect different aspects of an organism, for example, colour, height, shape, resistance or susceptibility to diseases.

  4. What is agricultural biotechnology?

    Agricultural biotechnology is a set of tools used to modify plants, animals and microorganisms for a specific purpose. For example, it may be used to improve resistance to pests and diseases, and increase nutrient content. Agricultural biotechnology employs a wide range of techniques including genetic engineering and plant breeding. Although several techniques are used in agricultural biotechnology, genetic engineering tends to receive the most attention from the public.

  5. Why genetically modify crops?

    When crops are improved by conventional breeding, new traits come from closely related species, for example a sorghum plant with another sorghum plant or a close relative. Genetic engineering allows for transfer of genes from different species. This is particularly valuable if genes encoding important traits such as pest or disease resistance are not available within the species. For instance, genes for stem borer resistance in maize were obtained from the bacterium Bacillus thuringiensis, and potential genes for bacterial wilt resistance in banana were obtained from sweet pepper. Genetic engineering can also be used if closely related species cannot be successfully cross pollinated, for example wild relatives of cowpea that contain pod borer resistance cannot successfully cross pollinate with the cultivated cowpea.

  6. Do genetically modified (GM) crops contain traits desired by farmers and consumers?

    Yes. For many centuries plant breeders have been crossing plants and transferring genes from one plant to another to introduce new useful traits such as disease resistance and improved yield. Genetic engineering has been used to transfer genes coding for desirable traits that are not available through conventional plant breeding.

    Examples of GM crops with traits valuable to farmers include: maize containing Bacillus thuringiensis (Bt) cry genes for resistance to stem borers; cotton containing Bt cry genes for resistance to bollworms; herbicide tolerant maize, and herbicide tolerant cotton. Scientists are also developing GM crops with consumer traits such as bananas with improved iron and beta carotene content; rice with improved beta carotene; and sorghum with improved iron, protein and beta carotene.

  7. Can GM traits be incorporated into locally adapted /farmer preferred crop varieties?

    Yes, GM traits can be incorporated directly into locally adapted/farmer preferred crop varieties. For example, Bt yellow maize expressing cry1Ab for controlling stalk borers was crossed with the economically important and farmer preferred South African white maize and an Egyptian local maize variety (Ajeeb).

  8. How long has genetic engineering/modification been used?
    The first products of genetic engineering used for food production were an enzyme used in cheese production and yeast used in baking. The products first appeared on the market in 1990, and are used widely in U.S, Europe and Asia. Genetically engineered bacteria and yeasts have also been used in the food industry for more than 20 years to produce vitamins and nutritional supplements. GE has been used to produce medicines, for example 90% of the insulin used to treat diabetes worldwide is produced by bacteria genetically engineered to express the human insulin gene. Genetic engineering is also used in the production of detergents and fuels.

    Farmers have been growing GM crops since 1996. Since then, the number of countries growing biotech crops has been increasing rapidly. 2012 was the seventeenth year of commercialization of biotech crops and, 28 countries now grow biotech crops including 20 developing countries in Africa, Asia, Australia and South America (

  9. How widely grown are GM crops?

    According to the International Service for the Acquisition of Agri-biotech Applications (ISAAA), the global area of biotech crops in 2013 was over 175 million hectares, grown by 18 million farmers in 27 countries. Biotech crops are grown in South America, North America, Europe, Asia, Australia and Africa. In Africa, South Africa, Burkina Faso and most recently Sudan grow biotech crops. Biotech crops grown in Africa include: herbicide tolerant soybean, Bt and herbicide tolerant cotton, and Bt and herbicide tolerant maize in South Africa; Bt cotton in Burkina Faso and Sudan; and Bt maize in Egypt. The different countries and biotech crops grown including adoption rates are reported annually by ISAAA (

  10. What are the benefits from GM crops?
      i. Improved yield and farm income

      GM crops with improved resistance to pests such as insect-resistant cotton and maize are less vulnerable to pests, hence produce higher yields, and the farmer gets higher farm income. Higher yields and increased farm income have been reported in developing countries such as Argentina, Mexico, India, South Africa and Burkina Faso. For instance, in India insect resistant cotton has contributed an additional 41% to cotton production, boosting farm income by $ 9,395.1 million; in South Africa, between 1998 and 2010 insect resistant maize and cotton have contributed an additional 12% and 24.1% to their production, thus boosting farm income by $769 million and $27.1 million respectively; and insect resistant cotton in Burkina Faso has contributed an additional 19% to cotton production between 2008 and 2010 (Brookes and Barfoot, 2012; Carpenter, 2010; Qaim et al., 2003; Qaim and Kathage, 2012; Raney, 2006).

      ii. Improved quality of crop produce

      Insect resistant GM crops such as Bt maize have resulted in better quality produce due to reduced pest damage that exposes cobs to fungal attack. The fungus produces mycotoxins that are highly toxic to humans and animals. Improved quality can result in less rejection of produce for sale, and improved health.

      iii. Reduced pesticide use, and positive environmental and health benefits

      Insect resistant GM crops have resulted in reduced pesticide use. As a result, the farmer spends less on pesticides. Reduced use has also resulted in positive environmental and human health benefits. The number of farmers reporting illness associated with application of pesticides has been reduced in developing countries that have adopted GM crops such as China, India and South Africa. Most farmers in developing countries apply pesticides without protective clothing using knapsack sprayers. Planting insect resistant GM crops has resulted in significant reduction in the use persistent synthetic pesticides that may contaminate ground water and the environment. For example, adoption of insect resistant maize in South Africa since 2000 has reduced the volume of insecticide active ingredient (ai) and the associated environmental load by 57%; adoption of insect resistant cotton in India since 2002 has reduced insecticide ai by 16.2% and the associated environmental load by 20.4%. Adoption of Bt cotton in Burkina Faso since 2008 has resulted in increased populations of bees important for pollination as a result of reduced pesticide use (Brookes and Barfoot, 2012; Carpenter, 2010; Qaim et al., 2003; Qaim and Krishna, 2012; Raney, 2006).

      iv. Reduced pest populations in other host plants

      Bt cotton and maize have also resulted in reduced pest populations on other nearby host crops, by preventing the survival of pest larvae to produce adults, which would have laid eggs on nearby host crops. These effects have been documented in China and U.S (Wu et al., 2008).

      v. Flexibility in weed management

      Herbicide tolerant crops like herbicide tolerant maize, soybean and cotton provide farmers with flexibility in weed management. Herbicide tolerant soybean grown in Argentina, Romania, South Africa and other countries has provided higher yields and profitability. Herbicide tolerant crops are also compatible with minimum tillage that protects the top soil from erosion (Brookes, 2005; Raney, 2006).

      vi. Future benefits

    GM crops under research and development such as rice and bananas with enhanced beta carotene content will help in reducing vitamin A deficiencies. Rice and maize with enhanced salt and drought tolerance will be able to better withstand saline and drought conditions.

  11. Do insect resistant GM crops cause new pest problems?

    Insect resistance

    Insect resistance is a natural evolutionary process enhanced by repeated exposure of the pest to high toxins. It can arise due to the widespread use of GM crops, and also with the widespread use of chemical pesticides on conventionally bred crops. Insect resistance to Bt can be slowed down by growing non-Bt crops (refugia) together with Bt crops, so that the resistant insects mate with susceptible ones. Other strategies that can slow down insect resistance include: stacking or pyramiding toxins that are distinct from each other, sterile moth releases, crop rotation and use of trap crops. Integrated pest management should not be neglected because no single method is sufficient.

    Emergence of minor or secondary pests as key pests

    Broad spectrum chemical pesticides typically kill primary pests, secondary pests and beneficial insects. Reduced use of broad spectrum pesticides that would have killed the secondary pest result in increased populations of secondary pests, for example increased mirid population sizes on Bt cotton in China. Integrated pest management practices such as crop rotation, biological control agents not targeted by the transgenes, tillage, intercropping, trap cropping should not be neglected by farmers (Bergé and Ricroch, 2010).

  12. Do herbicide tolerant GM crops cause new weed problems?

    Herbicide resistant weeds

    Glyphosate resistant weeds have been reported in U.S, Australia, Malaysia, East Asia and Chile. Emergence of glyphosate resistant weeds can result from selection pressure from repeated glyphosate applications, and if the rare resistant individuals in a weed population survive to produce progeny. Integrated weed management practices are important in managing evolution of herbicide resistant weeds. Such practices include: growing herbicide tolerant crops in rotation with conventional crops, tillage and use of other herbicides (Sandermann, 2006).

  13. Are GM crops safe for human / animal consumption?

    All biotech crops go through thorough testing before they are approved for commercial release to farmers and consumers. Researchers conduct more rigorous studies for biotech crops than those conducted for conventional crops to determine the safety of biotech crops. Regulatory and scientific agencies worldwide including the Food and Agricultural Organization (FAO) and the World Health Organization (WHO) who have reviewed the studies have confirmed the safety of biotech crops currently on the market (see also questions 19 and 20).

    GM crops are studied for potential changes in nutritional composition, toxicity and allergenicity. The studies conducted ensure that biotech crops are safe for human/animal consumption. People around the world have eaten foods containing biotech ingredients and no reliably documented human or animal safety issues have been reported since biotech crops were first grown in 1996.

  14. Do people eat GM crops?

    Yes, farmers in U.S, Argentina, Canada, Australia, Mexico and South Africa have been growing biotech crops like corn, soybean, sugar beets, canola, squash and papaya for more than 10 years. All these crops have been tested and proven safe to eat just like the conventional foods and ingredients.

  15. Do U.S consumers eat GM crops?

    U.S farmers produce GM sweet corn, papaya and squash for direct human consumption. Other GM crops grown include: field corn, sugar beet, soybean and canola. Many of the processed food products in U.S contain GM corn and soybean. Some GM field corn is used to make corn meal products like muffins, corn chips and tortillas, and to produce high fructose syrup used to sweeten soda pop and other drinks, and corn oil for cooking. GM soybeans are processed to produce oil used for cooking and soy lecithin, a product used in many foods. GM canola is processed into oil used for cooking. GM sugar beet is used to produce sugar found in many foods.

  16. Do people eat genes when eating GM crops?

    Yes, genes are part of all living organisms including conventionally bred plants and animals. People eat genes whenever they eat any kind of food.

  17. Are GM crops safe for the environment?

    The impacts of GM crops on the environment are assessed depending on the region or country and the crop. The new traits are evaluated to ensure that they do not cause weediness characteristics. Where GM crops are to be grown in proximity to related plants, the exchange of traits via pollen transfer is evaluated, and the impact of such pollen transfer is determined before release of the GM crop. Potential risks to birds, mammals, fish, pollinators such as bees, predators, parasitoids, decomposers such as earthworms and other beneficial organisms for pest or disease resistance traits are assessed to ensure there is no unintended harm with GM crops. No negative impacts to the environment relative to the production of non-GM crops have been reported.

  18. Who has reviewed the safety of GM crops?

    Table 1: Examples of regulatory agencies that have reviewed safety of GM crops

    Country/Region Agency
    Argentina National Agricultural Biotechnology Advisory Committee (environmental impact), National Service of Health and Agrifood Quality (food safety), National Agribusiness Direction (effect on trade), Secretariat of Agriculture, Livestock, Fishery and Food (makes final decision)
    Brazil National Biosafety Technical Commission (environmental and food safety), Council of Ministers (commercial and economical issues with release)
    Burkina Faso National Biosafety Agency
    China Office of Agricultural Genetic Engineering Biosafety Administration (OAGEBA)
    Eastern and Southern Africa Common Market for Eastern and Southern Africa (assesses environmental and food safety for 19 member countries but final decision for growing the GM crop is made by each individual country)
    Europe European Commission (EU), European Food Safety Authority (EFSA), final decision to use the GM crop is left to each EU member state.
    India Institutional Biosafety Committee (IBSC), Review Committee on Genetic Manipulation (RCGM), Genetic Engineering Approval Committee (GEAC) and Ministry of Agriculture
    South Africa Directorate of Biosafety of the Department of Agriculture, Forestry and Fisheries
    United States (U.S) U.S Department of Agriculture (environmental safety), Food and Drug Administration (food safety) and Environmental Protection Agency (safety of GM crops producing biopesticides)
  19. Which scientific agencies have examined the safety of GM foods?
    Scientific agencies from around the world, including North America, South America, Europe, Africa and Asia have examined the question of safety of GM foods. The International Council for Science comprising 111 National Academies of Science and 29 scientific unions has examined safety of GM foods. They state that “the main conclusion to be drawn from more than 130 research projects, covering more than 25 years of research and involving more than 500 research groups is that GM technologies are not per se risky than conventional plant breeding technologies, however decisions should be made case by case.”
  20. What is the role of the African Union in the use of biotechnology in Africa?
    African Union’s NEPAD agency strives to help African countries harness the new opportunities of biotechnology tools in the best and safest way to ensure food self-sufficiency and development for all. NEPAD’s African Biosafety Network of Expertise has thus been created with the mandate to support advancement of science and technology for agricultural development in Africa through the establishment of functional biosafety systems in African countries. ABNE services include information, training, education, and technical assistance related to the development of biosafety guidelines, standard operating procedures (SOPs) and implementing regulations. For more information, please click on the following link to download ABNE brochure:
  21. What is the status of crop biotechnology in Africa?
    19 out of 54 African countries have completed or are working to complete the process of biotechnology acquisition:

    1. Four countries are producing and commercializing GM crops: Burkina Faso, Egypt, Sudan and South Africa
    2. Four countries now have confined field trials (CFT) and biosafety laws: Cameroon, Ghana, Kenya and Malawi
    3. 2 countries have no biosafety laws but are implementing CFT: Nigeria and Uganda
    4. 9 countries have no CFT but have biosafety laws: Ethiopia, Mali, Mozambique, Namibia, Senegal, Tanzania, Tunisia, Zambia and Zimbabwe.


  22. What are the potential concerns about GM crops?
    • Does growing GM crops prevent export to Europe?

    Growing GM crops does not stop a country from exporting other agricultural products to Europe. U.S, Canada, Brazil, Argentina, Australia, China and South Africa grow GM crops such as maize, soybean, cotton, canola, sugar beet, papaya and squash ( but continue to export other agricultural products to Europe. They also export GM crops such as soybean that have been approved for use in Europe. In 2011, U.S, Canada, Brazil, Argentina, Australia, China and South Africa exported wheat and wheat flour, rice, fruits, vegetables and other agricultural products to Europe ( 2011/eu27-aggragate_en.pdf).

    • Do GM crops cause allergies?

    Genetic modification is a technique used to transfer genes encoding valuable traits into organisms. However, a GM crop could cause allergies if it was engineered with a gene that codes for a protein that causes allergies. Therefore the genes used are carefully tested to ensure that they do not produce allergenic proteins.

    • Won’t antibiotic resistance marker genes result in humans picking up antibiotic resistance?

    Antibiotic resistance markers used in the development of GM crops were selected by scientists based on safety criteria. The most widely used antibiotic resistance marker gene is nptII, which confers resistance to kanamycin and neomycin. This gene has been used to develop insect resistant and herbicide tolerant maize and cotton. The marker gene was selected based on the fact that kanamycin and neomycin are not important in medical treatment and about 20-40% of the naturally occurring bacteria in human and animal digestive tracts are already resistant to kanamycin and neomycin (EFB, 2001).

    The safety of GM crops containing antibiotic resistance marker genes has been thoroughly reviewed by experts from internationally recognized scientific bodies and committees in U.S, European Commission, Canada, Japan Switzerland and other countries. They concluded that the risk of gene transfer from GM crops to microbes is negligible and if it were to occur, there would be no impact due to the high frequency of antibiotic resistance in microbial populations (EFB, 2001; Read, 2000).

    However, due to the concerns that have been raised about the use of antibiotic resistance marker genes, scientists have developed alternatives for GM crop development. For instance, other selectable marker systems that rely on the growth of plant cells in the presence of growth regulators such as cytokinins are being used for the new GM crops coming to the market.

  23. Is Bt toxic to humans?
    Bt proteins have been widely demonstrated not to be toxic to humans, mammals, birds and fish. Bt crystal proteins are cleaved by proteolysis under alkaline conditions to toxic forms that are highly specific. The toxin binds to a specific receptor in the mid-gut of specific insects. These receptors are absent in mammals, birds and other animals. They are even specific to different kinds of insects. For example, Bt proteins that may protect plants against moths may not protect them against beetles.
References References

  1. Bergé, J.B and Ricroch, A.E. 2010. Emergence of minor pests becoming major pests in GE cotton in China. What are the reasons? What are the alternative practices to this change of status? GM crops, 1(4):214-219.
  2. Brookes, G and Barfoot, P. 2012. GM crops: global socio-economic and environmental impacts 1996-2010. PG Economics Ltd, UK. Dorchester, UK May 2012.
  3. Brookes, G. 2005. The farm-level impact of herbicide-tolerant soybean in Romania. AgBioForum, 8(4):235-241.
  4. Carpenter, J. 2010. Peer-reviewed surveys indicate positive impact of commercialized GM crops. Nature Biotechnology, 28(4): 319-321.
  5. European Federation of Biotechnology (EFB). 2001. Antibiotic resistance markers in genetically modified (GM) crops. Briefing Paper 10 September 2001.
  6. Qaim, M and Kathage, J. 2012. Economic impacts and impact dynamics of Bt (Bacillus thuringiensis) cotton in India. PNAS, 109:11652-11656.
  7. Qaim, M and Krishna, V.V. 2012. Bt cotton and sustainability of pesticide reductions in India. Agricultural Systems, 107:47-55.
  8. Qaim, M., Cap, E.J and de Janvry, A. 2003. Agronomics and sustainability of transgenic cotton in Argentina. AgBioForum, 6(1 and 2):41-47.
  9. Raney, T. 2006. Economic impact of transgenic crops in developing countries. Current Opinion in Biotechnology, 17:174-178.
  10. Read, D. 2000. Use of antibiotic resistance marker genes in genetically modified organisms. Environmental Risk Management Authority, New Zealand.
  11. Sandermann, H. 2006. Plant biotechnology: ecological case studies on herbicide resistance. Trends in Plant Science, 11(7):324-328.
  12. Wu, K., Lu, Y., Feng, H., Jiang, Y and Zhao, J. 2008. Suppression of cotton bollworm in multiple crops in China in areas with Bt toxin-containing cotton. Science, 321:1676-1678.