A scientist wants to produce a crop plant that is resistant to a particular herbicide. The scientist plans to use genetic engineering to insert a gene from a bacterium into the crop plant's genome. Explain how genetic engineering could be used to produce herbicide-resistant crop plants, and describe one potential benefit and one potential risk of releasing these genetically modified plants into the environment.
Written & reviewed by James Millett — Biology (Imperial College London), PGCE Science (University of Cambridge).
Genetic engineering allows scientists to transfer genes from one organism to another, creating organisms with new characteristics. Herbicide-resistant crop plants have been developed to allow farmers to spray fields with herbicides without harming the crop.
Model answer (5 marks)
1. The gene that confers resistance to the herbicide is identified in the bacterium and isolated using restriction enzymes.
2. The isolated gene is inserted into a plasmid vector that contains a plant promoter and a selectable marker.
3. The plasmid is introduced into the crop plant cells by Agrobacterium tumefaciens or particle bombardment.
4. The plant cells integrate the plasmid DNA into their genome and express the bacterial gene, producing the resistance protein.
5. The transgenic plants are selected, regenerated and grown; they can now survive herbicide application while normal crops cannot.
Benefit: farmers can spray herbicides to control weeds without damaging the crop, increasing yield and food production.
Risk: the resistance gene may spread to wild relatives or weeds through cross‑pollination, creating herbicide‑resistant ‘superweeds’ that are harder to control.
2. The isolated gene is inserted into a plasmid vector that contains a plant promoter and a selectable marker.
3. The plasmid is introduced into the crop plant cells by Agrobacterium tumefaciens or particle bombardment.
4. The plant cells integrate the plasmid DNA into their genome and express the bacterial gene, producing the resistance protein.
5. The transgenic plants are selected, regenerated and grown; they can now survive herbicide application while normal crops cannot.
Benefit: farmers can spray herbicides to control weeds without damaging the crop, increasing yield and food production.
Risk: the resistance gene may spread to wild relatives or weeds through cross‑pollination, creating herbicide‑resistant ‘superweeds’ that are harder to control.
Examiner tips
- Use the exact sequence of steps (gene isolation, vector construction, transformation, expression, selection).
- Show the benefit and risk clearly and link them to the question.
Mark scheme (5 marks)
- The gene for herbicide resistance is identified and cut from the bacterium's DNA
- The gene is inserted into the crop plant's genome / DNA
- The modified plant can now express the gene and produce the protein that confers herbicide resistance / the plant's phenotype is changed
- One benefit: increased crop yield / farmers can spray herbicides to kill weeds without damaging the crop, resulting in more food production
- One risk: the herbicide-resistance gene could spread to wild plant species / weeds via cross-pollination, creating 'superweeds' that are difficult to control
Key terms in this question
genetic engineering · genome · gene
Related
- All OCR A-Level Biology B — Advancing Biology (H422) revision notes →
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- Decode the mark scheme abbreviations →
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