IGCSE Biology / Genetic modification
GM crops, and the argument about them revision notes
Edexcel International GCSE Biology (4BI1), chapter 22: Genetic modification, specification point 5.15. Free lesson.
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Genetically modified (GM) crops have a gene from another organism inserted to give them a useful feature. They can help solve problems with food supply, pests and nutrition, but there are also risks to weigh before reaching a conclusion.
What makes a crop genetically modified
A GM crop has had a gene from another organism inserted into it. This differs from selective breeding, which uses only alleles already present in the species. GM changes can give crops features that help solve specific problems. Herbicide-resistant soya has a gene that makes it resistant to a herbicide. The whole field can be sprayed, killing the weeds while the crop survives. Insect-resistant maize has a bacterial gene that makes a protein toxic to certain insect larvae, so less insecticide is needed. Golden rice has genes that make its grains produce beta-carotene, which the…
What are the arguments in favour
GM crops may improve food supply and reduce some health and farming problems. The benefits depend on how the crop is used and where it is grown. Higher yields on the same land can help where food is short. Insect-resistant crops may need less pesticide sprayed. This can benefit other insects and the people applying the pesticide. Vitamin-enriched crops could help address nutritional problems. Drought- or salt-tolerant crops could grow on land that is difficult to farm.
What are the arguments against
Some concerns are about how GM traits might spread or change over time. Others relate to farmers’ access to seed and uncertainty about long-term effects. A herbicide-resistance gene could spread to wild relatives by pollination. If the plants are weeds, the herbicide may no longer control them. Insects may evolve resistance to the toxin made by an insect-resistant crop, making the benefit temporary. Farmers may become dependent on buying seed each year if a company owns the seed, rather than saving their own. The long-term effects of GM crops are not fully known. Public concern about…
How a resistance gene can escape
A gene can move between plants when pollen from a GM crop reaches and fertilises a wild relative. The offspring can inherit the resistance gene. If the wild relative is a weed, the herbicide may no longer control it, leaving farmers with fewer ways to manage it. Pollen can be carried from a GM crop to a nearby wild relative by wind or insects. The wild plant is fertilised and its offspring may inherit the gene.
How to structure an evaluation
For a question worth six marks, give points on both sides and finish with a conclusion. Weigh the arguments rather than simply listing them. Your conclusion should say which way you come down and why. Consider benefits such as higher yields, less pesticide, improved nutrition and farming land that is difficult to use. Balance these against gene escape, evolving insect resistance, dependence on seed companies and unknown long-term effects.