Genetic modification — Cambridge IGCSE Biology
Genetic modification: what it is, examples, how bacteria are modified to make a human protein, and GM crops.
Revision notes
3 short notes, in the order of the specification. Each one in short:
Genetic modification is changing the genetic material of an organism by removing, changing or inserting individual genes. The result is a genetically modified organism, often with a gene from another species. Examples include bacteria that make human insulin, herbicide-resistant and insect-resistant crops, and golden rice, which contains a vitamin A precursor to improve its nutritional quality.
Bacteria are genetically modified to make human insulin by cutting the human gene out of DNA with restriction enzymes, which leave sticky ends. A plasmid is cut with the same restriction enzymes, and DNA ligase joins the gene into it, forming a recombinant plasmid. This is inserted into bacteria, which multiply and express the gene, making the human protein.
GM crops: advantages and disadvantages
SupplementGM crops are crop plants such as soya, maize and rice that have been genetically modified, for example herbicide-resistant soya, insect-resistant maize and golden rice. Advantages include higher yields, less insecticide and better nutrition. Disadvantages include genes spreading to wild plants, harm to other organisms, expensive seed and pests becoming resistant to the toxin.
Exam questions
6 exam-style questions (16 marks), each with its mark scheme.
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Quick check questions
Define genetic modification.
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Changing the genetic material of an organism by removing, changing or inserting individual genes.
Give an example of a human protein made by genetically modified bacteria.
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Insulin.
Supplement Which enzyme cuts DNA to leave sticky ends?
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A restriction enzyme.
Supplement Which enzyme joins the gene into the plasmid?
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DNA ligase.
Supplement Name one disadvantage of GM crops.
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The gene may spread to wild plants; or it may harm other organisms.
Frequently asked questions
What is genetic engineering in agriculture?
Genetic engineering in agriculture means genetically modifying crop plants by inserting genes, often from another species. Examples are herbicide-resistant crops, which can be sprayed to kill weeds without being harmed, insect-resistant crops that need less insecticide, and crops with improved nutritional quality, such as golden rice, which contains a vitamin A precursor.
How is human insulin made by bacteria?
Supplement Human insulin is made by inserting the human insulin gene into bacteria. Restriction enzymes cut the gene out of human DNA, leaving sticky ends, and cut open a plasmid with matching sticky ends. DNA ligase joins the gene into the plasmid, making a recombinant plasmid. The bacteria multiply and express the gene, making insulin.
What do restriction enzymes and DNA ligase do?
Supplement Restriction enzymes cut DNA, leaving short single-stranded overhangs called sticky ends, while DNA ligase joins DNA. In genetic modification, the same restriction enzyme cuts out the human gene and cuts open the plasmid, so the sticky ends match. DNA ligase then joins the gene into the plasmid to form a recombinant plasmid.
What are the advantages and disadvantages of GM crops?
Supplement GM crops can give higher yields, because less is lost to weeds and insect pests, need less insecticide, and can improve nutrition, as with golden rice. However, genes may spread to wild plants, other organisms such as non-pest insects may be harmed, seeds can be expensive, and pests may become resistant to the toxin.
Written and checked against the Cambridge IGCSE Biology (0610) specification · Updated October 2026