An Introduction to Genetically Modified Crops

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What is the first impression you get when you hear “genetically modified” foods?

DNA is molecule of life


DNA contains all of instructions (genes) required to make an organism.

Genetically Modified Foods (GMF) involve the insertion of DNA from one organism into another OR modification of an organism’s DNA in order to achieve a desired trait.


Other Examples:

  • Golden rice – rice that contains beta-carotene (Vitamin A), which is not found in regular rice.
  • Bt corn – corn that contains a chemical normally found in a bacterium (Bacillus thuringiensis) that is toxic to insects but not to humans.
  • Herbicide resistant plants.

Modifying Genes:

These genes are also called recombinant DNA technology, molecular cloning, and genetic engineering.

  1. Restriction enzymes are used to “cut” DNA segments from one genome.
  2. DNA ligases are used to “paste” them into another genome.


How are animals targeted?

The microinjection method uses a fine needle to inject a solution of DNA into a developing embryo.


How are plants targeted?

Agrobacterium that normally normally infects plants with disease is used to infect plant with gene of interests. A particle gun is used to shoot small bits of metal coated with the gene into the plant.

How common are GM foods?

48 foods have been approved for use by the Canadian Food Inspection Agency.

Potential Benefits:

  1. Environmental:  reduced use of herbicides and chemicals in farming.
  2. Reduced effectiveness of pesticides as insects become resistant to engineered toxins.
  3. Loss of biodiversity

Potential Environmental Hazards:

Gene Transfer to non-target species.

  1. Herbicide resistant plants and weeds could cross breed and create “superweeds”
  2. To address this one could:
    • Create sterile male plants that don’t produce pollen
    • Engineer the plants so that pollen doesn’t contain the foreign genes
    • Create buffer zones of non-GM crops around GM crops.  The buffer crops would not be harvested.

Potential Human Health Risks:


  • Genetic engineering could potential introduce or create allergens
  • For example, inserting genes from a nut into another plant could be dangerous for people who are allergic to nuts

Unknown health risks

  • Biological processes involve a lot of INTERACTIONS

It is often difficult to identify every possible interaction

Economic Hazards:

Elimination of competition
 – GM seeds are patented

Suicide seeds
 – Plants with sterile seeds that are infertile are created
 – Farmers are forced to buy seeds every year

However, some companies have reduced costs or donated GM seeds to impoverished nations.

Creating a balance:

  • So are GM foods a good or bad thing?
  • It depends on each individual case.
  • Consumers, the government and scientists should be responsible for weighing the benefits against the costs.


  2. images/corn.jpg
  3. opg/images/dna.jpg
  4. GJOA/haven.html
  5. Fruitber.html
  6. images/microinjection.jpg
  7. jarq/32-4/hagio/fig4.htm
  9. Transgenic pollen harms monarch larvae (Nature, Vol 399, No 6733, p 214, May 1999)
  10. GM corn poses little threat to monarch (Nature Biotechnology, Vol 17, p 1154, Dec 1999) 
  11. monarch.html

@Shamaila Qasim
MSc Botany