5.3Use of Biological Resources
Genetic modification (genetic engineering) — Edexcel Modular - OL Revision Notes & Topical Questions
10 min read 8 parts Lesson 5 of 5 2 quizzes
Lesson summary
Genetic modification (genetic engineering) Edexcel O Level Modular Biology notes: understand how restriction enzymes are used to cut DNA at specific sites and ligase enzymes are used to join pieces of DNA togetherDNA is negatively charged because of phosphates.GMOs raise ethical …
- Insect-resistant crops
- Herbicide-resistant crops
- Golden rice
- Drought-resistant crops
- Why must the gene and the plasmid be cut with the same restriction enzyme?
- A student has to remember which enzyme cuts and which joins. Suggest a way to do it
Section 1 of 8Process & sequence
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Denature at 95 °C – strands separate.
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Anneal at ~55 °C – primers bind.
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Extend at 72 °C – Taq adds nucleotides.
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Repeat 30 cycles – doubles each time.
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DNA negative
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Moves to + electrode
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Small fragments farthest
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The human insulin gene is cut out of DNA using a restriction enzyme, leaving complementary sticky ends.
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A bacterial plasmid is cut with the same restriction enzyme, so its sticky ends match those of the gene.
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DNA ligase joins the gene into the plasmid, forming a recombinant plasmid.
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The recombinant plasmid is inserted into a bacterium.
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The bacterium divides rapidly, copying the plasmid and passing the insulin gene on to each new cell.
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The bacteria make human insulin from the gene they now carry.
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The bacteria are grown in a fermenter to produce large quantities, and the insulin is purified for use.
Making human insulinwrite these steps in this order; each step is a marking point.
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Restriction enzyme cuts out the human insulin gene
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Sticky ends are left on the gene
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Same restriction enzyme cuts the bacterial plasmid
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Ligase joins gene and plasmid into a recombinant plasmid
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Recombinant plasmid inserted into a bacterium
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Bacterium multiplies and copies the plasmid
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Insulin is made and harvested from the fermenter
Section 2 of 8Compare
| Technique | Purpose | Key steps | Enzyme / tool | Example use | Result |
|---|---|---|---|---|---|
| PCR | Copy DNA | 95 °C denature, 55 °C anneal, 72 °C extend | Taq polymerase | Forensics | Millions of copies |
| Gel electrophoresis | Separate fragments | Load, run current, stain | Agarose gel | DNA fingerprinting | Bands by size |
| Restriction digest | Cut DNA | Mix DNA + enzyme | Restriction enzymes | Cloning | Sticky ends |
| Bacterial transformation | Insert gene | Heat shock, select on antibiotic | Plasmid, ligase | Insulin production | GMO bacteria |
| Sequencing | Read DNA | Dideoxy / next-gen | DNA polymerase | Genome projects | Base sequence |
| CRISPR | Edit genes | Guide RNA targets DNA | Cas9 | Gene therapy research | Precise edit |
| Feature | GMO | Transgenic organism |
|---|---|---|
| New genetic material | Present | Present |
| Source of the DNA | May come from the same species | Comes from a different species |
| Relationship | The wider group | A sub-group of GMOs |
| Every transgenic organism is a… | — | GMO |
| Aspect | Advantages | Disadvantages |
|---|---|---|
| Chemicals used | Fewer pesticides and herbicides needed | Farmers become dependent on particular herbicides |
| Cost | Cheaper for farmers to grow | The seeds themselves are expensive |
| Yield | Increased yield | Some GM crops grow less well |
| Environment | Overall benefit from reduced chemical use | Gene transfer to wild relatives can reduce biodiversity |
Section 3 of 8Worked examples
1Why must the gene and the plasmid be cut with the same restriction enzyme?
- Because the same enzyme leaves the same complementary sticky ends on both pieces of DNA,
- so the exposed bases can pair and ligase can join them into one molecule.
2Restriction enzyme = scissors
A student has to remember which enzyme cuts and which joins. Suggest a way to do it.
- Restriction enzyme = scissors (it cuts DNA at a specific sequence);
- ligase = glue (it joins the cut pieces into one molecule).
3Give two concerns people raise about growing GM crops.
- Genes may transfer to wild relatives,
- reducing biodiversity and affecting wildflowers and insects;
- and reliance on specific herbicides may increase, with possible effects on human health.
- Seeds are also expensive for farmers.
4Explain how golden rice helps in a region where vitamin A deficiency is common.
- Golden rice is engineered to produce a precursor of vitamin A,
- so people whose diet depends on rice obtain vitamin A from the crop itself, preventing the deficiency.
Section 4 of 8Keep going
Genetic modification (genetic engineering) Edexcel O Level Modular Biology: what to do next
These Genetic modification (genetic engineering) Edexcel O Level Modular Biology notes covered the key ideas, worked examples and exam technique for this topic. Check your Genetic modification (genetic engineering) Edexcel O Level Modular Biology understanding with the practice questions below, then reread any Genetic modification (genetic engineering) Edexcel O Level Modular Biology point you were unsure about before moving on.
Genetic modification (genetic engineering) Edexcel O Level Modular Biology: revision checklist
1
Revise the main Genetic modification (genetic engineering) Edexcel O Level Modular Biology definitions until you can write them from memory.
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Practise Genetic modification (genetic engineering) Edexcel O Level Modular Biology exam questions under timed conditions.
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Link each Genetic modification (genetic engineering) Edexcel O Level Modular Biology idea to a diagram or a worked example.
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List the common Genetic modification (genetic engineering) Edexcel O Level Modular Biology mistakes and how to avoid them.
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Explain one Genetic modification (genetic engineering) Edexcel O Level Modular Biology idea out loud as if teaching a friend.
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Previous lesson: 5.2 Selective breeding — Notes
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Next lesson: 4.4 Cloning — Unit 2 Notes
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Course: Edexcel Modular - OL — all units
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Official syllabus: Pearson Edexcel International GCSEs
Section 5 of 8Key terms
Section 6 of 8Syllabus checklist
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understand how restriction enzymes are used to cut DNA at specific sites and ligase enzymes are used to join pieces of DNA together
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understand how plasmids and viruses can act as vectors, which take up pieces of DNA, and then insert this recombinant DNA into other cells
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understand how large amounts of human insulin can be manufactured from genetically modified bacteria that are grown in a fermenter
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understand how genetically modified plants can be used to improve food production
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understand that the term transgenic means the transfer of genetic material from one species to a different species
Section 7 of 8Command terms
Command terms
Give / State / Name
Recall a fact; one idea per mark.
Define
Give the exact meaning using the specification keywords.
Describe
Give an account of what happens / the pattern in data, quoting values; no reasons needed.
Explain
Give reasons with linked statements (cause → effect). Each linked step is usually a separate marking point.
Suggest
Use knowledge in a new context; more than one answer may be accepted.
Compare
Similarities and differences; each point must refer to both items.
Calculate
Show working; include units; check significant figures. Method marks are given even if the final answer is wrong.
Discuss
Explore the issue from different angles and link the points.
Evaluate / Assess
Weigh strengths and weaknesses and reach a supported judgement.
Deduce
Draw a conclusion from the information given.
Justify
Support a statement/choice with evidence.
Section 8 of 8Exam technique
Keywords the mark scheme looks for in this lesson
Keywords the mark scheme looks for in this lesson
PCR · Gel electrophoresis · Restriction enzyme · Plasmid vector · Transformation · DNA sequencing · CRISPR-Cas9 · GMO
Learn each definition in the Key words tab exactly; a missing keyword in a definition usually loses the mark.
How to get full marks (examiner guidance)
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Use specification keywords exactly (e.g. eukaryotic/prokaryotic, enzyme–substrate complex, active site, complementary).
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Link ideas
Link ideas for “explain” each marking point is usually a cause → consequence step; unlinked facts often score nothing.
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Use the information in the question
“discuss/evaluate” answers must use the data provided and match the number of marks.
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Convert units carefully (mg → g, cm³ → dm³) and show working for calculations.
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Avoid vague words
“it”, “stuff”, “things”, “goes up”, “energy is made”. Name the substance and the process.
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Do not extrapolate a graph line beyond the data or to zero unless asked.
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Six-mark extended responses are marked on content AND a logical, linked line of reasoning.
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Keywords the mark scheme looks for in this lesson
- Genetic modification — Restriction enzyme — Sticky ends — DNA ligase — Vector — Plasmid — Recombinant plasmid — Transgenic — Fermenter
- Name the enzymes exactly
- "restriction enzyme" for cutting and "ligase" for joining.
- "Enzyme" alone scores nothing.
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How the steps are marked
- For "explain how the insulin gene is put into a bacterium", one mark is usually given for each correct ordered step;
- write the sequence rather than a paragraph of general points.
- Always state that the same restriction enzyme is used for gene and plasmid, and give the reason: complementary sticky ends.
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Evaluation questions
- Use both sides of the argument from the Comparison table: fewer pesticides and higher yield against herbicide dependency, expensive seeds, poorer growth of some crops,
- and gene transfer reducing biodiversity.
- Precise examples score: golden rice = vitamin A precursor; insect-resistant wheat and maize = bacterial toxin gene.
Marked practiceQuizzes for this lesson
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