OCR GCSE Biology A: Genetic engineering and biotechnology in food production (J247) – Revision Notes

Use these notes for fast recall. The study guide has the full explanations and worked examples. They are aligned to the OCR GCSE (9-1) Gateway Science Biology A (J247) specification, Version 4.0 (August 2026), for first assessment in 2018, and cover B6.2d, B6.2e, B6.2f and B6.2g. Only B6.2e is Higher Tier only. Related pages: OCR GCSE Biology hub, printable checklist, practice questions and the free diagnostics.

Key definitions (B6.2d)

Term	Meaning
Genome	All the genetic material of an organism
Genetic engineering	A process that modifies the genome of an organism to introduce desirable characteristics
Transgenic	Carrying a gene from another species
GM (genetically modified)	An organism whose genome has been changed by genetic engineering
Desirable characteristic	A useful feature, such as insect resistance, added nutrients or faster growth

Remember: the change is in the genome, so it is inherited.

Key terms for the steps (B6.2e, Higher Tier only)

Term	Job
Restriction enzyme	Cuts DNA at one particular base sequence
Sticky ends	Short unpaired ends left by the cut; they pair with complementary ends
Vector	Carries the gene into the host cell (for example a plasmid)
Plasmid	Small circular loop of DNA, separate from the main chromosome
Ligase	Joins the gene and plasmid by sealing the sugar-phosphate backbones
Recombinant plasmid	Plasmid containing the new gene
Host bacteria	Cells that take up the plasmid and copy it
Antibiotic resistance marker	Gene on the plasmid that lets only plasmid-carrying bacteria grow on antibiotic agar

Method in steps (Higher Tier only)

1. Isolate the gene.
2. Cut the gene out with a restriction enzyme, leaving sticky ends.
3. Cut the plasmid with the same enzyme.
4. Mix and join with ligase to make a recombinant plasmid.
5. Add the plasmid to host bacteria.
6. Grow on agar with antibiotic; only transformed bacteria form colonies.

Two points to keep: the same enzyme must be used on gene and plasmid, and the marker shows plasmid uptake, not that the right gene is present.

Worked reminder

After treatment with plasmid, 36 colonies grew on antibiotic agar. Untreated bacteria on plain agar gave 120 colonies. Proportion transformed = 36 / 120 × 100 = 30.0%. Control plate with untreated bacteria on antibiotic agar should show no colonies; that shows the antibiotic works.

Benefits and risks (B6.2f)

Benefits	Risks
Higher yield	Gene flow to wild relatives or other crops
Fewer insecticide sprays for toxin-making crops	Pest resistance may evolve
Added nutrients	Harm to non-target organisms
Tolerance of drought, salt or herbicide	Unknown long-term effects, concern over health
Less food waste	Cost of seed and control by a few companies

• Practical considerations: cost, testing, regulation, keeping GM and non-GM crops separate, saving seed.
• Ethical considerations: moving genes between species, labelling and consumer choice, ownership, fairness to poorer farmers.
• Misconception to avoid: genetic engineering does not always raise pesticide use. Toxin-making crops can cut insecticide sprays, while herbicide-tolerant crops can raise herbicide use.

Genetic modification as a solution (B6.2g)

Type	Example	How it helps feed more people
GM crop	Insect-resistant crop	Less crop lost to pests
GM crop	Beta-carotene rice	Improves diet quality where vitamin A is low
GM livestock	Fast-growing salmon	Reaches market size sooner
GM microorganism	Bacteria making chymosin	Steady enzyme supply for cheese making

Useful calculations: percentage change = change / original × 100; share = part / whole × 100.

Worked reminders for data questions (B6.2f and B6.2g)

Percentage change. A GM variety yields 4.4 tonnes per hectare against 4.0 for the conventional one. Change = 4.4 − 4.0 = 0.4. Percentage change = 0.4 / 4.0 × 100 = 10% higher. Always divide by the original (here conventional) value.

Reading a table. If a table shows insecticide sprays falling from 5 to 2, say both numbers and the difference: “sprays fell from 5 to 2, a drop of 3, which is 60%”. Quoting the figures is what turns a general statement into evidence.

Reading a graph. Say what each axis shows, describe the overall trend, quote two values with units, then add a pattern such as “faster after year 5”. Do not claim a cause that the graph cannot show: a rise in GM area does not by itself prove the GM crop raised yields.

Cost and benefit. Income = yield × price. Profit = income − seed cost − spray cost. Compare both crops on the same area of land, and say the answer applies only to the figures given.

Faster growth. If a GM animal reaches market size in 15 months and the conventional one takes 24, time saved = 9 months, which is 9 / 24 × 100 = 37.5%. Linking this to more animals produced per year in the same space gives the food-supply point.

How to write a good evaluation (B6.2f)

An evaluation answer usually has four parts:

1. A benefit with a reason. “Insect-resistant maize makes its own toxin, so less of the crop is eaten and yield rises.”
2. A risk with a reason. “Pollen may carry the gene to wild relatives, which could pass the trait to weeds.”
3. A practical or ethical point. “Seed may need buying afresh each season, a cost that small farms could find hard to meet.”
4. A judgement. “On balance, the benefit is greater where pests cause large losses, as long as resistance is monitored.”

Use specific examples rather than “it is good” or “it is bad”. Use comparison words such as “whereas” and “however” to show you are weighing the two sides.

Examples of GM in food production (B6.2g)

• Crops: insect-resistant (toxin gene from a bacterium), herbicide-tolerant, nutrient-enriched (beta-carotene rice), drought-tolerant.
• Livestock: a salmon with a growth hormone gene that reaches market size sooner.
• Microorganisms: bacteria or fungi that make a protein in a fermenter, such as chymosin for cheese making or insulin for people with diabetes.
• Why these matter: the population is growing, farmland is limited, so each hectare, plant and animal must deliver more food or lose less to pests and disease.

When asked to “explain how”, always finish the chain: the gene gives the characteristic, the characteristic raises yield or cuts losses, and that means more food from the same resources.

Must-know distinctions

• Selective breeding vs genetic engineering: selective breeding chooses parents within a species over many generations; genetic engineering changes the genome directly and can use a gene from another species.
• Restriction enzyme vs ligase: one cuts, one joins.
• Plasmid vs chromosome: plasmid is a small separate loop.
• Vector vs host: the vector carries the gene; the host is the cell that receives it.
• Benefit vs risk: always say who gains or is harmed.

Quick self-test

1. State what is meant by genetic engineering.
2. Name the enzyme that cuts DNA at a specific sequence. (Higher Tier only)
3. Name the enzyme that joins the gene to the plasmid. (Higher Tier only)
4. What are sticky ends, and why do they matter? (Higher Tier only)
5. Why is an antibiotic resistance gene put on the plasmid? (Higher Tier only)
6. Give one benefit and one risk of an insect-resistant crop.
7. A trial finds yield rises from 5.0 to 6.0 tonnes per hectare. Calculate the percentage increase.
8. A GM crop covers 18 million hectares of a country’s 120 million hectares of cropland. What percentage is this?
9. Explain why GM crops do not always lead to more pesticide use.
10. Suggest one ethical concern about genetic engineering in farming.

Answers

1. A process that modifies the genome of an organism to introduce desirable characteristics.
2. Restriction enzyme.
3. Ligase.
4. Short unpaired ends left by a restriction enzyme. They pair with complementary sticky ends on DNA cut by the same enzyme, so the gene can join the plasmid.
5. It is a marker: only bacteria that took up the plasmid survive on agar containing the antibiotic.
6. Benefit: fewer insecticide sprays or higher yield. Risk: pests may become resistant, or non-target insects may be harmed.
7. (6.0 − 5.0) / 5.0 × 100 = 20%.
8. 18 / 120 × 100 = 15%.
9. Crops making their own insect toxin can reduce the need for insecticide sprays. (Herbicide-tolerant crops may do the opposite, so it depends on the trait.)
10. Any one: moving genes between species is unnatural; consumers may lack choice without labelling; a few companies may control seed; poorer farmers may not afford it.

Where marks are usually lost

• Writing “ligase cuts” or “restriction enzymes join”.
• Forgetting that the same restriction enzyme cuts both gene and plasmid.
• Saying the antibiotic resistance gene helps the plant, when it is a marker for bacteria.
• Describing a benefit without linking it to food supply, or a risk without saying what harm could follow.
• Stating that all GM crops use more pesticide, or that none do.
• Leaving out units, or giving a percentage change without dividing by the original value.
• Evaluating with a one-sided list instead of reaching a judgement.
• Using “gene” and “genome” as if they meant the same thing.

Official syllabus

OCR GCSE (9-1) Gateway Science Biology A (J247), specification Version 4.0 (August 2026), for first assessment in 2018, published by OCR. Statements B6.2d to B6.2g.