CIE A Level Biology (9700) 2019-2021

Revision Notes

19.3.1 Genetically Modified Organisms in Agriculture

Significance of Use in Agriculture

  • Genetic engineering is a technique used to deliberately modify a specific characteristic (or characteristics) of an organism. The technique involves removing a gene (or genes) with the desired characteristic from one organism and transferring the gene (using a vector) into another organism where the desired gene is then expressed
  • The genetically engineered organism will then contain recombinant DNA and will be a genetically modified organism (GMO)
  • Although plants and animals have been genetically engineered to produce proteins used in medicines the main purpose for genetically engineering them is to meet the global demand for food
  • Crop plants have been genetically modified to be:
    • Resistant to herbicides – increases productivity / yield
    • Resistant to pests – increases productivity / yield
    • Enriched in vitamins – increases the nutritional value
  • Farmed animals have been genetically modified to grow faster. It is rarer for animals to be modified for food production due to ethical concerns
  • Scientists have genetically modified many organisms including bacteria (eg. to produce insulin), sheep (eg. to produce a human blood protein known as AAT), maize (eg. to be resistant to insect attacks), rice (eg. to produce β-carotene to provide vitamin A)
  • The benefits of using genetic engineering rather than the more traditional selective breeding techniques to solve the global demand for food are:
    • Organisms with the desired characteristics are produced more quickly
    • All organisms will contain the desired characteristic (there is no chance that recessive allele may arise in the population)
    • The desired characteristic may come from a different species / kingdom
  • There are consequences of using genetically engineered organisms to solve the global demand for food, although many are still being researched:
    • The development of resistance for the genes that have been introduced
    • The risk of the gene spreading to wild relatives
    • The modified organism may become a pest
    • The reduction in biodiversity
    • Potential ecological effects (eg. harm to non-targeted species like the Monarch butterflies)

Bt maize

  • Maize (also known as corn) is a cereal crop that is mainly grown as a source of feed for animals, but is also used in the manufacture of pharmaceutical (as a base for antibiotics) and industrial products (eg. production of ethanol) and for human consumption
  • Maize has been genetically modified with a gene for a toxin. The toxin is called Bt toxin as it was taken from the bacterium Bacillus thuringiensis
  • The significance of genetically engineering maize to be insect resistant is that there is an increase in yield (although insects have developed resistance to the Bt toxin genes). Another advantage of growing Bt maize is that less pesticides are used which could have ecological benefits (eg. non-targeted invertebrates not harmed) and could mean

GM salmon

  • In 2015 AquaAdventure Salmon was approved by the US Food and Drug Authority (FDA) for human consumption
  • This salmon has been genetically modified (GM) to grow more rapidly than non-GM salmon as a result of growth hormone being produced in the salmon throughout the year, instead of just in spring and summer. The producer therefore has a product to sell in half the time, which increases their yield
  • Scientists combined a growth hormone gene from a chinook salmon with the promoter gene from an ocean pout, a cold-water fish. The ocean pout fish can grow in near-freezing waters, thus the promoter gene ensured the growth hormone was continually being expressed
  • To prevent the GM salmon from reproducing in the wild, all the salmon are female and sterile

Exam Tip

Understand the advantages and disadvantages of genetically modifying organisms so that you can explain the significance of genetically engineering crop plants and livestock.

Author: Catherine

Cate has over 20 years’ experience teaching Biology to IGCSE, IB and A-level students in seven different countries across Asia, Europe, North America and the Middle East. This has given her a fine appreciation of different cultures, places and teaching methods. Cate has a keen interest in producing Biology revision resources that will help students engage with the subject.
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