Scientists have used genetic engineering to insert a gene into salmon that causes them to grow much faster than normal. Explain the process used to insert the growth gene into the salmon's genome.
Written & reviewed by James Millett — Biology (Imperial College London), PGCE Science (University of Cambridge).
Farmers who raise salmon for food are interested in using genetically engineered salmon because the fish reach market size in half the usual time. The growth gene originally came from a different species of fish.
Model answer (5 marks)
1. Identify the growth gene in the donor fish DNA.
2. Use restriction enzymes to excise the gene from the donor DNA.
3. Insert the gene into a suitable vector (e.g. plasmid or viral vector).
4. Use DNA ligase to seal the gene into the vector.
5. Transfer the recombinant vector into salmon cells so the gene integrates into the salmon genome and is expressed.
2. Use restriction enzymes to excise the gene from the donor DNA.
3. Insert the gene into a suitable vector (e.g. plasmid or viral vector).
4. Use DNA ligase to seal the gene into the vector.
5. Transfer the recombinant vector into salmon cells so the gene integrates into the salmon genome and is expressed.
Examiner tips
- Use the exact sequence of steps; each point counts as one mark.
- Mention the role of restriction enzymes and ligase explicitly.
- Show the vector as the delivery vehicle.
- Explain that integration leads to expression in the salmon.
Common mistakes
- Omitting the restriction enzyme step.
- Confusing the vector with the salmon cell itself.
- Failing to state that the gene becomes part of the salmon genome.
Mark scheme (5 marks)
- The desired growth gene is identified / located in the donor organism's DNA
- Restriction enzymes are used to cut out the growth gene from the donor DNA
- A vector (such as a plasmid or virus) is used to carry / transfer the gene
- Ligase enzyme is used to join / seal the growth gene into the vector
- The vector transfers the gene into the salmon's cells so it becomes part of the salmon's genome and is expressed
Key terms in this question
Related
- All OCR A-Level Biology B — Advancing Biology (H422) revision notes →
- How to answer a "Explain" question →
- Decode the mark scheme abbreviations →
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