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

This study guide is aligned to the OCR GCSE (9-1) Gateway Science Biology A (J247) specification, Version 4.0 (August 2026), for first assessment in 2018. It covers statements B6.2d, B6.2e, B6.2f and B6.2g in topic B6.2, Feeding the human race. Statement B6.2e is in bold in the specification, so it is Higher Tier only; the other three are assessed in both tiers. Food security, agricultural solutions and selective breeding (B6.2a to B6.2c) have their own pages and are not repeated here.

Links: OCR GCSE Biology hub, printable checklist, revision notes, practice questions and the free 10-minute diagnostics.

What this unit covers

Statement	What you must be able to do	Tier
B6.2d	Describe genetic engineering as modifying the genome of an organism to introduce desirable characteristics	Both
B6.2e	Describe the main steps: restriction enzymes, sticky ends, ligase, vectors such as plasmids, host bacteria, selection using antibiotic resistance markers	Higher Tier only
B6.2f	Explain benefits and risks of gene technology in modern agriculture, including practical and ethical considerations	Both
B6.2g	Describe and explain genetic modification as a biotechnological solution to the demands of a growing human population	Both

The maths covered here is extracting and interpreting information from charts, graphs and tables (the specification’s mathematical learning outcome for this topic). Every worked example below uses invented, illustrative figures.

B6.2d: What genetic engineering is

The genome is all the genetic material of an organism. Genetic engineering is a process that modifies the genome of an organism to introduce desirable characteristics. In practice a gene that gives a useful feature is moved from one organism into another, so the receiving organism can make a protein it could not make before. An organism that carries a gene from another species is called transgenic.

Desirable characteristics in food production include:

• a crop plant that makes a toxin harmful to certain insect pests (Bt crops use a gene from the bacterium Bacillus thuringiensis)
• a crop that makes a nutrient it normally lacks, such as rice modified to make beta-carotene, which the body can convert to vitamin A
• a crop that tolerates a herbicide, so weeds can be sprayed without killing the crop
• an animal that grows faster, such as a salmon carrying a growth hormone gene
• a microorganism that makes a useful protein, such as insulin or a cheese-making enzyme

Because the change is made to the genome, the new characteristic is inherited. Offspring receive the gene too, which is why a farmer can keep growing the improved organism.

Genetic engineering is not the same as selective breeding. Selective breeding picks parents with useful features from within a species and takes many generations. Genetic engineering changes the genome directly, can use a gene from a different species and gives the characteristic in one generation of the modified organism.

B6.2e: The main steps (Higher Tier only)

You need the order of the steps and the job done at each one.

1. Identify and isolate the gene that codes for the desired characteristic.
2. Cut it out using a restriction enzyme. Each restriction enzyme cuts DNA at one particular base sequence. Many leave a short stretch of unpaired bases on each end of the cut. These are sticky ends.
3. Cut the vector with the same restriction enzyme. A vector carries the gene into the host cell. A common vector for bacteria is a plasmid, a small circular loop of DNA separate from the main chromosome. The same enzyme gives the plasmid sticky ends that match the ones on the gene.
4. Join them with ligase. The sticky ends pair by complementary bases (A with T, C with G). DNA ligase seals the sugar-phosphate backbones. The result is a recombinant plasmid.
5. Put the plasmid into host bacteria. The bacteria take up the plasmid and may then copy it each time they divide.
6. Select the bacteria that took it up. The plasmid used also carries an antibiotic resistance marker gene. When the bacteria are grown on agar containing that antibiotic, only bacteria carrying the plasmid survive and form colonies.

The sticky ends are the key idea. Two pieces of DNA cut by the same enzyme have ends that are complementary, so they join. DNA cut by different enzymes would not match.

Worked example: reading a selection experiment

A technician treats bacteria with a plasmid that carries a resistance gene for antibiotic K, then spreads the same volume of culture onto agar plates.

Plate	Bacteria	Antibiotic K in agar	Colonies
1	not treated with plasmid	no	210
2	not treated with plasmid	yes	0
3	treated with plasmid	yes	42

Plate 1 shows the bacteria are alive and able to grow. Plate 2 shows that untreated bacteria cannot survive antibiotic K, so any colony on plate 3 must have gained resistance. Plate 3 colonies each carry the plasmid, so each is a transformed bacterium. Using plate 1 as the number of cells that could grow, the proportion transformed is 42 / 210 × 100 = 20.0%.

A limit to remember: the marker shows that the plasmid was taken up. It does not by itself prove the gene you wanted is inside it, so further tests are needed.

B6.2f: Benefits and risks in modern agriculture

Examine each claim and ask who gains, who might be harmed, and what evidence supports it.

Possible benefits	Possible risks
Higher yield from the same land, because pests damage less of the crop	Genes could pass by pollination to wild relatives or non-GM crops
Fewer insecticide sprays on crops that make their own toxin	Pests may evolve resistance to the toxin, making it less useful over time
Crops with added nutrients, helping where diets lack them	Effects on non-target organisms, such as harmless insects, are possible
Crops that tolerate drought, salt or herbicide	Some people worry about long-term effects on health, and some crops may increase herbicide use
Longer shelf life and less waste	Seeds can be costly and may be controlled by a few companies

A common misconception is that genetic engineering always means more pesticide. It does not. A crop that makes its own insect toxin can mean fewer insecticide sprays. A herbicide-tolerant crop, however, may lead to more herbicide use, and weeds can evolve resistance to it. Judge each crop on its own trait.

Practical considerations include cost of seed, whether farmers can save seed, the need for testing and regulation, and keeping GM and non-GM crops apart. Ethical considerations include whether it is right to move genes between species, whether consumers can choose through labelling, who owns the technology, and fairness to poorer farmers.

Worked example: evaluating a trial

A trial compares two types of cotton field. Figures are per hectare per season. Cotton is valued at 1200 currency units per tonne, and each insecticide spray costs 12 units.

	Conventional	Insect-resistant GM
Mean yield (tonnes)	1.8	2.3
Insecticide sprays	6	2
Seed cost (units)	40	95

• Yield change: (2.3 − 1.8) / 1.8 × 100 = 27.8% higher.
• Sprays: 6 − 2 = 4 fewer.
• Conventional: 1.8 × 1200 = 2160; 2160 − 40 − (6 × 12 = 72) = 2048 units.
• GM: 2.3 × 1200 = 2760; 2760 − 95 − (2 × 12 = 24) = 2641 units.

The GM crop gives 593 more units per hectare, even with the dearer seed. A balanced evaluation adds that this is one trial: it does not show effects on wildlife, pest resistance over many years or a farmer’s access to credit for seed.

B6.2g: Genetic modification as a biotechnological solution

The specification asks you to describe and explain how genetic modification could meet the demands of a growing human population. The central argument is simple: more people need more food, and there is limited new farmland, so each hectare, plant and animal has to deliver more.

GM crops. Insect-resistant, disease-resistant, drought-tolerant and nutrient-enriched crops all aim to raise the amount of food from the same land or reduce losses. Rice modified to make beta-carotene targets vitamin A deficiency, which is a problem of diet quality as well as quantity.

GM livestock. One example is a salmon carrying a growth hormone gene from another salmon species, controlled by regulatory DNA from a different fish. It grows faster early in life, so it reaches market size sooner, though it ends up no larger as an adult.

GM microorganisms. Bacteria or fungi given a gene can make a protein in industrial fermenters. Chymosin, an enzyme used in cheese making, was traditionally taken from calf stomachs. Making it in modified microorganisms gives a steady supply that does not depend on slaughter.

Evidence for these claims often comes as charts and tables, so practise reading them.

Worked example: interpreting adoption data

The table shows invented figures for the area of GM crops in one country, where the total area of cropland is 18 million hectares.

Year	GM crop area (million hectares)
2010	1.2
2015	3.0
2020	5.4

• Increase from 2010 to 2020: 5.4 − 1.2 = 4.2 million hectares, which is 4.2 / 1.2 × 100 = 350%.
• Mean increase per year: 4.2 / 10 = 0.42 million hectares per year.
• Share of cropland in 2020: 5.4 / 18 × 100 = 30%, up from 1.2 / 18 × 100 = 6.7%.

Growth was faster in the second five years (2.4 against 1.8 million hectares), so adoption was speeding up.

For the salmon example, suppose a conventional fish takes 28 months to reach market size and a GM fish takes 16 months. The time saved is (28 − 16) / 28 × 100 = 42.9%. That means the same tank space can produce more fish per year, which is the food-supply argument. The matching risk is escape: faster-growing fish that breed with wild fish could change wild populations.

Common errors

• Writing that restriction enzymes “join” DNA. Restriction enzymes cut; ligase joins.
• Saying a plasmid is part of the main chromosome. It is a separate small loop.
• Describing sticky ends as sticky because of glue. They are single-stranded ends whose bases pair with complementary bases.
• Claiming antibiotic resistance markers are there to kill bacteria. They let you select the bacteria that took up the plasmid.
• Calling every GM crop a pesticide user, or saying GM crops are harmless. Both are too general.
• Giving only an advantage when asked to evaluate. Weigh both sides, then reach a judgement.
• Mixing up the genome of the organism with the gene inserted.

Next steps

Work through the revision notes, then try the practice questions. The OCR GCSE Biology checklist lets you tick off each statement, and the diagnostics find weak spots.

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, topic B6.2 Feeding the human race.