Genetically modified organisms in agriculture

· Genetically modified organisms (GMOs) = organisms whose genetic material has been deliberately altered using genetic engineering.
· In agriculture, genetic engineering can improve quality and productivity of crop plants and farmed animals.
· GMOs may help meet the global demand for food by increasing yield, reducing crop losses, improving growth rate, or improving food quality.
· Key CIE examples: GM salmon, herbicide-resistant soybean, and insect-resistant cotton.
· Exam questions often ask for both benefits and ethical/social implications, so avoid one-sided answers.

GM salmon

· GM salmon are genetically engineered to grow faster than non-GM farmed salmon.
· The salmon contain a growth hormone gene from Chinook salmon controlled by a promoter from ocean pout.
· This allows the growth hormone gene to be expressed for more of the year, so salmon reach market size more quickly.
· Agricultural advantage: faster growth can increase productivity in aquaculture and may help meet demand for animal protein.
· Possible benefit: less time and resources may be needed per fish produced.
· Possible concern: if GM salmon escape, they could compete with wild salmon or affect wild gene pools, although containment and sterility are used to reduce this risk.
· Exam focus: link the genetic modification to faster growth, food supply, and ethical/environmental concerns.

The diagram shows how a promoter from ocean pout and a growth hormone gene from Chinook salmon are used to produce GM salmon. It helps students connect the inserted genes to faster growth and increased aquaculture productivity. Source

Herbicide-resistant soybean

· Herbicide-resistant soybean plants are genetically modified so they survive application of a specific herbicide.
· The herbicide kills weeds, but the soybean crop remains alive.
· Agricultural advantage: farmers can control weeds more effectively, reducing competition for light, water, mineral ions and space.
· Reduced weed competition can increase crop yield and make food production more efficient.
· Possible benefit: easier weed control may reduce labour and improve farm efficiency.
· Possible concern: repeated herbicide use can select for herbicide-resistant weeds, making weed control harder over time.
· Social concern: farmers may become dependent on specific seed companies or herbicide systems.
· Exam focus: explain that the modified crop survives herbicide, while weeds are killed, improving productivity.

This diagram shows the key idea behind herbicide-resistant crops: the GM plant survives herbicide treatment while susceptible plants die. It is useful for explaining how weed control can improve crop productivity. Source

Insect-resistant cotton

· Insect-resistant cotton is genetically modified to produce a protein toxic to specific insect pests.
· The common example is Bt cotton, which contains a gene from the bacterium Bacillus thuringiensis.
· The inserted Bt gene codes for a toxin that kills certain insect larvae, such as cotton pests.
· Agricultural advantage: reduced insect damage increases cotton yield and improves productivity.
· Possible benefit: farmers may use less chemical insecticide, reducing costs and environmental impact.
· Possible concern: insect populations may evolve resistance to Bt toxin if selection pressure is high.
· Possible concern: effects on non-target organisms and biodiversity should be monitored.
· Exam focus: link the inserted Bt gene to insect resistance, reduced crop damage and increased yield.

The image shows a gene from Bt bacteria being inserted into cotton DNA to create insect-resistant cotton. It directly supports the CIE example of insect resistance in cotton. Source

Benefits of GMOs in food production

· GMOs can increase food supply by improving yield, growth rate, and resistance to pests or weeds.
· GM crops may reduce losses caused by insects, weeds, and environmental pressures.
· GM animals or crops may improve quality, such as growth performance, nutritional composition or farming efficiency.
· GM crops can reduce use of some chemical pesticides if the crop is engineered for insect resistance.
· Higher productivity can help farmers produce more food from the same land area.
· Exam answers should always connect the benefit to solving global food demand, not just describe the modification.

Ethical and social implications of GMOs

· Food safety concerns: some people worry about possible long-term effects of consuming GMO foods.
· Environmental concerns: transgenes could spread to wild relatives, or GMOs could affect non-target species.
· Resistance concerns: pests may evolve resistance to Bt toxin, and weeds may evolve herbicide resistance.
· Biodiversity concerns: widespread use of a small number of GM varieties may reduce genetic diversity in crops.
· Economic concerns: GM seeds may be expensive, increasing dependence on biotechnology companies.
· Labelling and consumer choice: some people believe GMO foods should be clearly labelled.
· Ethical concerns: some people object to moving genes between species, especially in animals.
· Social benefit: GMOs may help improve food security, especially where crop losses are high.
· Strong exam answers must discuss both advantages and risks, then give a balanced conclusion.

Exam comparison: three CIE examples

· GM salmon → faster growth → increased aquaculture productivity → concern about escape, welfare and effects on wild salmon.
· Herbicide-resistant soybean → crop survives herbicide → weeds killed → increased yield → concern about resistant weeds and herbicide use.
· Insect-resistant cotton → produces Bt toxin → insect pests killed → reduced crop damage → concern about resistant insects and non-target organisms.
· The phrase “quality and productivity” is central: quality may include improved farming efficiency or product characteristics; productivity means more output per unit time, land or resource.
· When asked to “discuss”, include benefits, risks, social factors, ethical issues, and a justified judgement.