International A Level Biology / Gene technology
Genetically modified organisms: risks and benefits revision notes
Edexcel International A Level Biology (YBI11), chapter 25: Gene technology, specification point 8.22. Free lesson.
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Genetically modified organisms (GMOs) can bring benefits such as higher yields and useful medicines, but they can also create risks for ecosystems, people and farmers. In an evaluation, use the named organism and data, explain a relevant benefit and risk, then make a judgement.
What benefits can GMOs provide?
A GMO has changed DNA, often by receiving a gene from another species. Benefits depend on the organism and the gene it carries, so link each point to the example named in a question. Pest resistance: Bt maize and Bt cotton have a gene from the bacterium *Bacillus thuringiensis*. It makes a toxin that kills caterpillars, so farmers can use less insecticide. Herbicide resistance: Herbicide-tolerant soya survives weedkiller. The weeds are killed while the crop grows, which can increase yield. Higher yield: Controlling pests and weeds means less crop is lost, so more food can be…
What risks can GMOs create?
For each risk, explain what happens and why it matters. Avoid vague claims such as saying only that a GMO is unethical. State who or what is affected. Gene transfer: Pollen can carry a gene, such as herbicide resistance, to a wild relative. The resulting weeds may not be killed by that herbicide. Resistance: If pests meet the same Bt toxin repeatedly, resistant pests may survive and breed. Weeds can also become resistant when the same herbicide is used repeatedly. Food webs: Fewer weeds can mean less food for birds. Bt toxin could also harm insects that are not pests.…
How does resistance spread?
Bt toxin does not cause pests to mutate. Mutations happen randomly, and a few pests may already carry an allele, which is a version of a gene, that gives resistance. The toxin kills susceptible pests, leaving resistant ones more likely to reproduce. Resistant pests survive and pass the resistance allele to their offspring. Over generations, the allele becomes more common through natural selection.
How do you use data in an answer?
Calculate percentage change by comparing the change with the original value, then multiply by 100. A negative answer shows a decrease.
How do you write a balanced evaluation?
An evaluation needs both sides and a judgement. Keep every point tied to the organism, its gene and the evidence given. For Bt cotton, the Bt toxin gene kills bollworms, the caterpillars that eat cotton. For the Bt cotton data, yield rose by 27.8% and insecticide sprays fell by 62.5%. Fewer sprays can also spare other insects. A relevant risk is that bollworms could become resistant to the Bt toxin, so the benefit may not last. A judgement should weigh these points. For example, the benefits are large now, but they will last only if resistance is slowed.
How does the context change the answer?
A good answer is specific, not a statement that could apply to any GMO. For a GM salmon with an extra growth hormone gene from another fish, reaching market size in about half the normal time means more fish can be produced in the same time and space. This could provide cheaper food. If salmon escape, they could outcompete wild salmon for food or breed with them and pass on the gene.