By the end of this lesson
- Describe examples of genetically modified crops.
- Explain how each modification can improve food production.
- Evaluate possible benefits and risks of GM crops.
BIG QUESTION
Could changing a crop’s genes feed more people?
GM crops may increase yield or nutrition, but whether they do depends on the trait, the place and how they are managed.
Pest-resistant crops
A gene from the bacterium Bacillus thuringiensis codes for a Bt toxinA protein, made by the bacterium Bacillus thuringiensis, that kills insect larvae that eat it; its gene is put into some crops. that kills some insect larvae. When inserted into crops such as maize or cotton, the plants make the toxin themselves.
Insects that eat the crop die, so less crop is damaged and farmers may spray less insecticideA pesticide that kills insects..
Herbicide-resistant and nutritionally improved crops
herbicide-resistantDescribes a crop, often genetically modified, that is not killed by a particular herbicide, so the herbicide can kill weeds around it. crops survive a herbicide that kills surrounding weeds, so weeds compete less for light, water and minerals and yield may increase.
Crops can also be modified for nutrition. Golden riceRice genetically modified to make beta-carotene in its grains, which the body converts into vitamin A. contains genes that lead to beta-carotene production, which the body uses to make vitamin A.
Possible concerns
Concerns include genes spreading to wild relatives by pollen, insects becoming resistant to Bt toxin, effects on non-target insects and reduced biodiversity if weeds are removed completely.
The evidence for some risks is still debated, and impacts may differ between crops and regions, so conclusions should be conditional.
Types of GM crop
Each trait solves a different food-production problem.
| Modification | How it improves food production | Possible concern |
|---|---|---|
| Bt pest resistance | Less insect damage; less insecticide sprayed. | Insects may evolve resistance; non-target insects affected. |
| Herbicide resistance | Weeds removed without harming crop. | Reduced weed biodiversity; resistant weeds may develop. |
| Golden rice | Source of beta-carotene for vitamin A. | Cost, acceptance and diet diversity issues. |
Language that earns precision
- Bt toxin
- An insecticidal protein from the bacterium Bacillus thuringiensis.
- herbicide resistance
- The ability of a plant to survive a chemical weedkiller.
- GM crop
- A crop plant whose DNA has been altered by genetic engineering.
- biodiversity
- The variety of species in an area.
Common misconceptions
Claim: Eating GM crops changes your genes.
Correction: Digested DNA does not alter the DNA in your cells.
Claim: GM crops always increase yield.
Correction: They may increase yield where the targeted problem limits growth; effects vary.
Claim: Bt crops kill all insects.
Correction: The toxin affects certain insect groups that eat the crop.
Match the answer to the command word
Name the modification, the problem it solves and how this may increase yield or nutrition.
Use may, could and depends; include at least one benefit and one risk with reasons.
Recall, apply, then justify
Explain how inserting a Bt toxin gene into maize can increase yield.
Hint
Toxin → insects → crop damage.
Suggested marking points
- The maize produces a toxin that kills insect pests (larvae).
- Less of the crop is eaten / damaged.
- More crop is harvested (or less insecticide is needed).
Give two possible concerns about growing herbicide-resistant crops.
Hint
Weeds and wildlife.
Suggested marking points
- Gene could spread to wild relatives / weeds become herbicide resistant.
- Reduced biodiversity because weeds and the animals depending on them are removed.
Discuss whether growing GM pest-resistant crops is good for the environment.
Planning hint
Balance and conditional language.
What a strong design includes
- Less insecticide may be sprayed.
- Fewer harmful effects on non-target organisms from sprays.
- Higher yields may reduce the land needed for farming.
- Pests may evolve resistance to the toxin.
- Non-target insects feeding on the crop may be harmed.
- Genes may spread to wild plants; overall effect depends on crop and management.