5.3Use of Biological Resources
Genetic Modification (Genetic Engineering) — Edexcel International GCSE Biology 4BI1 Revision Notes & Topical Questions
10 min read 8 parts Lesson 3 of 7 1 quiz
Lesson summary
Genetic Modification (Genetic Engineering) Edexcel IGCSE Biology 4BI1 notes: Describe the use of restriction enzymes, ligase and vectors.The genetic code is universal, so bacteria can read a human gene and make the human protein.The same restriction enzyme must cut both the gene …
- DNA ligase
- Manufacturing insulin
- Food production benefits
- GMO vs transgenic
- Why plasmids are useful vectors
- Explain why the same restriction enzyme is used to cut both the human DNA and the plasmid
Part 1 of 8Key ideas
1
The genetic code is universal, so bacteria can read a human gene and make the human protein.
2
The same restriction enzyme must cut both the gene and the plasmid so the sticky ends match.
3
Human insulin from GM bacteria is used to treat type 1 diabetes.
4
Bacteria are used because they reproduce rapidly and are easy to grow.
5
Bt crops contain a gene from Bacillus thuringiensis that makes a protein toxic to insect larvae.
6
GM plants can be made by using a bacterium or virus vector to insert genes into plant cells, which are then grown by tissue culture.
Part 2 of 8Learning objectives
1
Describe the use of restriction enzymes, ligase and vectors.
2
Describe how human insulin is produced using GM bacteria.
3
Describe examples of GM plants and their use in food production.
4
Evaluate the benefits and risks of genetic modification.
Part 3 of 8Essential knowledge
Essential knowledge
Genetic modification
Genetic modification a gene for a desired characteristic is taken from one organism and inserted into another. The organism receiving the gene is transgenic. This works because all organisms use the same DNA code.
Restriction enzymes
Restriction enzymes recognise specific base sequences and cut DNA there, often in a staggered way producing sticky ends. Using the same enzyme on the donor DNA and the plasmid gives complementary sticky ends that can pair up.
DNA ligase
DNA ligase seals the gene into the cut plasmid, forming recombinant DNA. The plasmid acts as a vector; viruses can also be vectors.
Manufacturing insulin
Manufacturing insulin the recombinant plasmid is taken up by bacteria.
- These are grown in large fermenters with controlled temperature, pH, nutrients and oxygen.
- The bacteria divide rapidly and each produces human insulin, which is extracted and purified.
- This gives a reliable, large supply of insulin identical to human insulin.
GM plants
GM plants genes can be inserted into crop plants to give resistance to insect pests (reducing insecticide use), resistance to herbicides (so fields can be sprayed to kill weeds), tolerance of drought or salt, or improved nutritional value (e.g. golden rice producing beta-carotene).
Food production benefits
Food production benefits higher yields, less crop loss, less use of chemical sprays, and more nutritious food, helping feed a growing population.
Concerns
Concerns possible transfer of genes to wild plants creating herbicide-resistant weeds, effects on insects and food chains, reduced biodiversity, unknown long-term health effects, and high cost of seed for farmers.
GMO vs transgenic
Any organism whose DNA has been artificially altered is a GMO. It is transgenic only if the new DNA came from a different species, so every transgenic organism is a GMO but not every GMO is transgenic.
Why plasmids are useful vectors
Plasmids are separate from the main bacterial chromosome, so they are easy to remove, alter and put back. Each time a bacterium divides, its plasmids are copied, so every daughter cell inherits the inserted gene.
Part 4 of 8Process & sequence
- Identify and cut out the human insulin gene using a restriction enzyme.
- Cut a bacterial plasmid with the same restriction enzyme, producing matching sticky ends.
- Mix gene and plasmid; DNA ligase joins them to form recombinant DNA.
- Insert the recombinant plasmid into a bacterium.
- Grow the transgenic bacteria in a fermenter where they multiply.
- Bacteria express the gene and make human insulin, which is extracted and purified.
Making human insulinwrite these steps in this order; each step is a marking point.
- Cut insulin gene out
- Cut plasmid open
- Ligase joins gene into plasmid
- Plasmid enters bacterium
- Bacteria grow in fermenter
- Insulin extracted and purified
Part 5 of 8Worked examples
1Complementary sticky ends
Explain why the same restriction enzyme is used to cut both the human DNA and the plasmid.
- Each restriction enzyme cuts at a specific base sequence and leaves particular sticky ends.
- Using the same enzyme gives the gene and plasmid complementary sticky ends, so they can base pair and be joined by DNA ligase.
2Identical to human insulin
Give two advantages of producing insulin with GM bacteria rather than extracting it from animal pancreases.
- 1) The insulin is identical to human insulin, so fewer allergic reactions.
- 2) Bacteria reproduce rapidly, so large quantities can be made reliably and cheaply, without using animals.
Part 6 of 8Summary
- GM organisms containing foreign genes are transgenic.
- Restriction enzymes cut DNA; ligase joins it.
- Plasmids are vectors carrying genes into bacteria.
- GM bacteria make human insulin in fermenters.
- GM crops can be pest-resistant or herbicide-resistant.
Part 7 of 8Keep going
Genetic Modification (Genetic Engineering) Edexcel IGCSE Biology 4BI1: what to do next
These Genetic Modification (Genetic Engineering) Edexcel IGCSE Biology 4BI1 notes covered the key ideas, worked examples and exam technique for this topic. Check your Genetic Modification (Genetic Engineering) Edexcel IGCSE Biology 4BI1 understanding with the practice questions below, then reread any Genetic Modification (Genetic Engineering) Edexcel IGCSE Biology 4BI1 point you were unsure about before moving on.
Genetic Modification (Genetic Engineering) Edexcel IGCSE Biology 4BI1: revision checklist
- Revise the main Genetic Modification (Genetic Engineering) Edexcel IGCSE Biology 4BI1 definitions until you can write them from memory.
- Practise Genetic Modification (Genetic Engineering) Edexcel IGCSE Biology 4BI1 exam questions under timed conditions.
- Practice: Genetic Modification (Genetic Engineering) Edexcel IGCSE Biology 4BI1 practice questions
- Previous lesson: 5.2 Selective Breeding — Notes
- Next lesson: 5.4 Cloning — Notes
- Course: Edexcel International Gcse Biology 4BI1 — all units
- Official syllabus: Pearson Edexcel International GCSEs
Part 8 of 8Compare: Compare
| Tool | Role |
|---|---|
| Restriction enzyme | Cuts the gene out and cuts the plasmid open at the same sequence |
| DNA ligase | Joins the gene into the plasmid |
| Plasmid / virus | Vector carrying the gene into the host cell |
| Host bacterium | Multiplies rapidly and expresses the gene |
| Fermenter | Grows large numbers of GM bacteria to make the product |
| Modification | Benefit | Concern |
|---|---|---|
| Pest resistance (Bt toxin gene) | Less insecticide, higher yield | Pests may evolve resistance; harm to non-target insects |
| Herbicide resistance | Weeds killed without harming crop | Genes may spread to wild relatives |
| Golden rice (vitamin A precursor) | Reduces vitamin A deficiency | Cost, reduced variety |
| Drought tolerance | Grows in dry areas | Unknown long-term effects |
Key terms
Command 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.
Exam technique
Keywords the mark scheme looks for in this lesson
Keywords the mark scheme looks for in this lesson
Genetic modification · Transgenic organism · Restriction enzyme · DNA ligase · Plasmid · Vector · Sticky ends · Recombinant DNA · Fermenter
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)
How to get full marks (examiner guidance)
Use specification keywords exactly (e.g. eukaryotic/prokaryotic, enzyme–substrate complex, active site, complementary).
Link ideas
Link ideas for “explain” each marking point is usually a cause → consequence step; unlinked facts often score nothing.
Use the information in the question
“discuss/evaluate” answers must use the data provided and match the number of marks.
Convert units carefully (mg → g, cm3 → dm3) and show working for calculations.
Avoid vague words
“it”, “stuff”, “things”, “goes up”, “energy is made”. Name the substance and the process.
Do not extrapolate a graph line beyond the data or to zero unless asked.
Six-mark extended responses are marked on content AND a logical, linked line of reasoning.
Marked practiceQuizzes for this lesson
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