CSEC BIOLOGY · SECTION C · LESSON C7

Genetic Engineering

How genes are transferred between organisms, uses in medicine and agriculture, and the advantages, disadvantages and ethical issues.

Continuity and VariationSO C 6.1SO C 6.2≈ 30 min🎮 3 games
Before you start

By the end of this lesson you can…

1WatchExplainer video 2ReadNotes & worked examples 3PractisePaper 1 style 4ApplyPaper 2 style
Step 1 · Watch

Explainer video

6 narrated scenes. Press play, listen and read along — the points appear as they are explained. Use ‹ Prev / Next › or the scene bar to jump to any scene.

LESSON C7 · EXPLAINER

Genetic Engineering

Since the 1980s, the insulin used by people with diabetes has increasingly been made by microorganisms — bacteria or yeast — carrying a human gene.

Narration uses your device’s built-in voice. No sound? Switch to “Captions only” — the captions advance on their own.

Step 2 · Read

Key notes

Copy these into your notebook in your own words — that is how they stick.

Genetic engineering

Direct manipulation of DNA, e.g. transferring a gene from one organism to another.

Tools

Restriction enzymes (cut), ligase (join), vector (plasmid or virus).

Insulin production

Gene cut out → inserted into plasmid → bacterium → fermenter → insulin.

Uses

Insulin, growth hormone, vaccines, clotting factors; pest/drought/virus-resistant crops; Golden Rice; gene therapy.

Advantages

Pure human proteins; higher yields; less pesticide; crops for harsh conditions; speed.

Disadvantages

Gene spread to wild species; effect on non-target organisms; health concerns; patents/cost; ethical objections.

vs artificial selection

Both for human benefit; GE is direct, fast, cross-species; AS uses existing variation over generations.

EXAM TIPS & COMMON MISTAKES

  • Insulin by GE involves ALL of: transfer of the human gene, a vector (plasmid), and production by the bacterium.
  • In the stages diagram, insulin is produced at the LAST stage (bacteria containing the recombinant plasmid).
  • For an ethical/ecological implication, explain it: e.g. “pollen from GM corn could fertilise wild relatives, spreading the gene”.
Step 2 · Learn from examples

Worked examples & study resources

The kind of support a teacher gives after the lesson: worked examples to attempt first, a board illustration, key terms, common misconceptions and memory aids.

Worked example 1

Making a virus-resistant crop

Scientists want to make papaya plants resistant to a virus disease by giving them a gene from the virus coat. Outline the steps, naming the tools used.

Try it in your notebook first, then reveal the solution one step at a time.

  1. Identify and isolate the useful gene (here, a gene for the virus’s coat protein).
  2. Cut it out with a restriction enzyme, which cuts DNA at specific sequences, leaving “sticky ends”.
  3. Cut open a vector (e.g. a bacterial plasmid) with the same restriction enzyme so the sticky ends match.
  4. Join the gene into the plasmid with the enzyme DNA ligase — this is recombinant DNA.
  5. Transfer the plasmid into papaya cells (for example using a bacterium that infects plants), grow the cells into whole plants, and select the plants that carry and express the gene.
Answer. Identify gene → cut out with restriction enzyme → insert into plasmid (vector) cut with the same enzyme → join with ligase → transfer into plant cells → grow and select genetically modified plants.
Examiner’s tip. Name the enzymes: restriction enzyme cuts, ligase joins. A real example: virus-resistant GM papaya helped save Hawaii’s papaya industry from papaya ringspot virus.
Worked example 2

Writing a balanced “discuss” answer

Discuss whether a Caribbean country should allow farmers to grow genetically modified (GM) crops. [6 marks]

Try it in your notebook first, then reveal the solution one step at a time.

  1. “Discuss” means give points FOR and AGAINST, then reach a judgement.
  2. Arguments for: higher yields; crops resistant to pests or disease, so fewer pesticides are sprayed; crops that tolerate drought — useful as climate change brings longer dry seasons; more nutritious varieties.
  3. Arguments against: genes might spread to wild relatives by cross-pollination; reduced genetic variety if only a few GM varieties are grown; possible effects on other organisms (e.g. insects that are not pests); seeds may be expensive and controlled by a few companies; some consumers and export markets reject GM food.
  4. Conclude with a reasoned judgement: e.g. GM crops could be allowed case by case, after testing for safety and environmental effects, with clear labelling.
Answer. A strong answer gives about three advantages and three disadvantages, each explained, and ends with a reasoned conclusion.
Examiner’s tip. Each point must be explained (“…so fewer pesticides are needed, reducing harm to wildlife”), not just listed. Balance and a conclusion are what lift the mark in a “discuss” question.
On the board · Genetic engineering and artificial selection
Genetic engineeringArtificial selection
HowA specific gene is cut out and inserted into another organism’s DNAHumans choose parents with desired features and breed them
SpeedFast — one generationSlow — many generations
Genes between species?Yes (e.g. human gene into bacteria)No — only within a species
PrecisionOne known geneMany genes; unwanted features can come too
ExamplesInsulin from bacteria; GM papaya; Bt cornHigh-yield cattle; sugar cane varieties; dog breeds

Both change the genes of organisms for human benefit — but in very different ways.

Key terms

Genetic engineering
Changing an organism’s DNA by inserting a gene from another organism.
Restriction enzyme
Enzyme that cuts DNA at a specific base sequence.
DNA ligase
Enzyme that joins pieces of DNA together.
Plasmid
A small ring of DNA in a bacterium, often used as a vector.
Vector
Something used to carry a gene into a cell, e.g. a plasmid or virus.
Recombinant DNA
DNA made by joining DNA from two different sources.
GMO
Genetically modified organism.

Common misconceptions

  • ✗ Eating GM food will change your own genes.✓ Digestion breaks the DNA in all food down into small molecules; it does not enter your genes.
  • ✗ Genetic engineering and cloning are the same.✓ Cloning makes genetically identical copies; genetic engineering changes the DNA by adding a gene.
  • ✗ Changing crops’ genes is brand new.✓ People have changed crops by artificial selection for thousands of years; genetic engineering is the newer, faster method.

Memory aid

Cut (restriction enzyme) → Paste (ligase) → Copy (bacteria multiply the recombinant DNA).

Real-life link

Since the 1980s, human insulin for people with diabetes has been made by genetically modified bacteria and yeast. In the Caribbean, where diabetes is very common, this provides a reliable, affordable supply of insulin.

Try this

Choose one GM product (e.g. insulin, GM papaya, Bt corn). Make a one-page fact sheet: what gene was added, from which organism, and one benefit and one concern.

Play & practise

Games

3 quick games on this lesson. Earn XP and badges as you play — your best score for each game is saved. Games are for practice and do not change your exam readiness.

Step 3 · Practise

Paper 1 practice — multiple choice

8 items modelled on real CSEC Paper 1 questions. Choose one answer for each, then check. Aim for 80% or better.

Adapted from CSEC P1 May/June 2022, Item 60

1. Which are involved in producing insulin by genetic engineering? I Transfer of the human insulin gene to a bacterium II A vector to transfer the gene III Production of insulin by the bacterium

Answer: D. All three steps are required.
Adapted from CSEC P1 May/June 2023, Item 60

2. In a diagram of insulin production (I plasmid removed; II gene cut from human DNA; III recombinant plasmid; IV bacterium with recombinant plasmid), insulin is produced at stage

Answer: D. Only a living bacterium with the gene makes insulin.
EduTech practice item (SO C6.1)

3. The enzyme used to cut DNA at specific places is

Answer: A. Ligase joins DNA.
EduTech practice item

4. In genetic engineering, a plasmid acts as a

Answer: A. It carries the gene into the bacterium.
EduTech practice item (SO C6.2)

5. Which is a possible DISADVANTAGE of GM crops?

Answer: B. Gene flow could create superweeds.
Based on CSEC P2 January 2026, Q4(d)(i)

6. One way genetic engineering and artificial selection are similar is that both

Answer: C. Both are human-directed.
Based on CSEC P2 January 2022, Q1(e)

7. The diamondback moth pest strain created by researchers differs from moths with a new wing colour because it

Answer: C. Engineered vs spontaneous variation.
EduTech practice item

8. Insulin made by GM bacteria is preferred to animal insulin because it

Answer: B. It is human insulin.
Step 4 · Apply

Paper 2 practice — structured questions

Write full answers, then reveal the mark scheme and tick the points you earned (19 marks in total). Your answers are saved on this device.

Based on CSEC P2 January 2026 (hybrid), Question 4

Question 1 [12 marks]

Farmers ask your biotechnology company whether to use artificial selection or genetic engineering to produce drought-tolerant corn.

(a) Define genetic engineering and artificial selection, and state THREE ways genetic engineering is used. [5]

MARK SCHEME — (a) (max 5)

(b) State ONE similarity and TWO differences between genetic engineering and artificial selection. [5]

MARK SCHEME — (b) (max 5)

(c) Explain ONE ethical or ONE ecological implication the farmers should consider. [2]

MARK SCHEME — (c) (max 2)

Based on SO C6.1 and CSEC P1 2023 Item 60

Question 2 [7 marks]

People with type 1 diabetes need insulin.

(a) Describe how bacteria can be genetically engineered to produce human insulin. [5]

MARK SCHEME — (a) (max 5)

(b) Give TWO advantages of producing insulin this way. [2]

MARK SCHEME — (b) (max 2)

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Sources

Where this topic appears in CSEC papers

Find these in your own past-paper booklets for extra timed practice. The practice above is adapted from them.