OCR GCSE Biology A: Monoclonal antibodies, aseptic technique and drug development (J247) – Revision Notes

These condensed notes cover OCR GCSE (9-1) Gateway Science Biology A (J247), Version 4.0 (August 2026), statements B6.3m, B6.3n, B6.3p and B6.3q. B6.3m and B6.3n are printed in bold in the specification, so they are Higher Tier only. For full explanations read the study guide, then test yourself with the practice questions. More links: OCR GCSE Biology hub, checklist and the free diagnostics.

Key terms

Term	Meaning
Antigen	A molecule, usually on a pathogen or cell, that the immune system recognises
Antibody	Protein made by a B lymphocyte; its binding site fits one antigen
Monoclonal antibody	Identical antibodies from one clone of cells, all binding the same antigen
Hybridoma	A cell made by fusing a B lymphocyte with a tumour cell
hCG	Hormone in the urine of a pregnant woman, detected in pregnancy tests
PSA	Protein in blood that can be raised in prostate cancer, measured with monoclonal antibodies
Aseptic technique	Methods that keep unwanted microorganisms out of a culture and your culture out of the surroundings
Autoclave	Steam sterilisation under pressure
Preclinical testing	Laboratory cell, computer and animal tests before any human use
Clinical trial	Testing of a drug on people, in phases
Placebo	A dummy treatment that looks like the real drug
Double-blind	Neither patients nor doctors know who gets the drug

B6.3m Making monoclonal antibodies (Higher Tier only)

Method in steps:

1. Inject the antigen into a mouse.
2. Take B lymphocytes making the antibody (often from the spleen).
3. Fuse them with tumour cells to make hybridomas.
4. Screen to select hybridomas making the required antibody.
5. Clone the selected cells and grow them in large amounts.
6. Collect and purify the antibody.

Why both parent cells: the lymphocyte gives specificity (one antibody), the tumour cell gives unlimited division. The hybridoma gives both.

B6.3n Uses of monoclonal antibodies (Higher Tier only)

Use	How it works	Key point
Pregnancy test	Antibodies on a strip bind hCG in urine; beads gather at the test line	Control line shows the test worked
Detecting disease	Antibodies bind a marker such as PSA in blood, or carry a label to show where an antigen is	A raised PSA is a reason for more tests, not proof
Cancer treatment	Antibody carries a drug to antigens on cancer cells	Less harm to healthy cells, still potential and costly

Pregnancy test read-out:

Test line	Control line	Meaning
Coloured	Coloured	hCG present
Absent	Coloured	hCG not detected
Either	Absent	Test invalid, repeat

B6.3p Aseptic technique

Technique	Purpose
Alcohol on bench and hands	Kills microorganisms on surfaces
Autoclave glassware and media	Steam under pressure, about 121 °C, kills all microorganisms and spores
Flame the loop and bottle neck	Sterilises the loop, and the air current at the neck carries contaminants away
Work near a Bunsen burner	Upward air current carries microorganisms away from dishes
Lid lifted slightly, briefly	Fewer microorganisms fall in
Tape the lid in a few places	Keeps the lid on but lets oxygen in
Incubate around 25 °C (schools)	Avoids conditions that suit human pathogens
Uninoculated control plate	Shows whether sterile technique worked

Contamination: wrong organisms grow, so results cannot be trusted and a pathogen could be spread.

B6.3q New medicines

1. Discovery: from plants, microorganisms or made by chemists, then screened.
2. Preclinical: cells and tissues, computer models, live animals. Checks toxicity, effect and dose.
3. Phase 1: small number of healthy volunteers, safety and dose.
4. Phase 2: small number of patients, effectiveness and dose.
5. Phase 3: large number of patients, compared with a placebo or the current treatment.
6. Approval, then continued monitoring.

Trial design points: random allocation, placebo, double-blind, large sample, informed consent. Thalidomide shows why testing, including use in pregnancy, matters.

Maths reminders

Skill	Rule	Example
Area of circular colony	πr², r is half the diameter	Diameter 4.0 cm gives r = 2.0 cm, area = 12.6 cm²
Area of clear zone around a disc	π(R² − r²)	R = 12 mm, r = 3 mm gives 424 mm²
Percentage	part ÷ whole × 100	6 of 40 plates contaminated is 15%
Percentage change	(new − old) ÷ old × 100	8.0 to 5.2 is a 35% decrease
Scatter diagram	Describe the trend; correlation is not proof of cause	Higher dose with more side effects is a positive correlation
Sampling	A larger, random, representative sample gives more reliable results

Worked reminders

Cross-sectional area of a culture. A colony has a diameter of 15 mm. Step 1: r = 15 ÷ 2 = 7.5 mm. Step 2: area = π × 7.5² = 177 mm² (3 significant figures).

Clear zone around a disc. An antibiotic disc has a diameter of 6 mm and the clear zone has a diameter of 14 mm. Clear area around the disc = π × (7² − 3²) = π × 40 = 126 mm².

Comparing groups in a trial. In a trial with 150 patients on the new drug, 9 had side effects (6.0%). With 150 on the existing drug, 4 had side effects (2.7%). The new drug has the higher rate, but a rate from 9 people is a small number, so a larger trial is needed before concluding it is less safe.

Must-know distinctions

Compare	Point
Antibody and antigen	The antibody is the protein from a B lymphocyte; the antigen is the molecule it binds
One clone, one target	Monoclonal means one clone and one binding site, so only one antigen is targeted
Lymphocyte and tumour cell in a hybridoma	Lymphocyte gives the specific antibody; tumour cell gives repeated division
Test line and control line	Test line shows hCG; control line shows the strip worked
Diagnosis and treatment uses	Detection labels or measures an antigen; treatment carries a drug to a target
Sterilising and disinfecting	Autoclave and flame sterilise equipment; alcohol cleans a surface or skin
Preclinical and clinical	Preclinical uses cells, models and animals; clinical uses people
Phase 1 and phase 3	Phase 1 is safety in few healthy people; phase 3 is effectiveness in many patients
Placebo and double-blind	Placebo is the dummy treatment; double-blind hides who has what from patients and doctors

Evaluation points for longer answers

For monoclonal antibodies, benefits include specific targeting, quick results from pregnancy tests and the possibility of fewer side effects in cancer treatment. Limitations include cost, that not every cancer has a suitable antigen, and that treatment is still being developed.

For animal testing in drug development, arguments for are that it shows effects on a whole body before people are exposed. Arguments against are animal suffering and the fact that an animal does not always respond as a human does.

For clinical trials, arguments for include protecting the public from harmful drugs. Arguments against include the time and cost, which delay patient access, and the risk to volunteers. A balanced answer gives a point from each side and ends with a judgement.

Quick self-test

1. Name the two types of cell fused to make a hybridoma. (Higher Tier only)
2. Why can a hybridoma make large amounts of antibody? (Higher Tier only)
3. Which hormone does a pregnancy test detect? (Higher Tier only)
4. What does the control line show? (Higher Tier only)
5. Give one reason a raised PSA does not prove prostate cancer. (Higher Tier only)
6. Why is a drug attached to a monoclonal antibody less harmful to healthy cells? (Higher Tier only)
7. Why is the neck of a bottle passed through a flame?
8. Give one reason the lid of a Petri dish is not completely sealed.
9. A colony has a diameter of 15 mm. Calculate its area to 3 significant figures.
10. Why is a placebo used in a phase 3 trial?
11. A cell count falls from 8.0 × 10⁵ to 5.2 × 10⁵. Calculate the percentage change.
12. Who takes part in a phase 1 trial and why?

Answers

1. A B lymphocyte (antibody-producing white blood cell) and a tumour cell.
2. It divides without limit like the tumour cell and makes the one antibody like the lymphocyte.
3. hCG.
4. That the test worked, because the antibodies there bind the mobile antibodies whether or not hCG is present.
5. Other prostate conditions can also raise PSA, so it needs further tests.
6. The antibody binds antigens on cancer cells, so the drug is delivered to them and fewer healthy cells are exposed.
7. It sterilises the neck and moves air upward, which stops contaminants entering.
8. So oxygen can enter and dangerous anaerobic bacteria are less likely to grow.
9. r = 7.5 mm. Area = π × 7.5² = 177 mm².
10. So that any improvement caused by expectation or natural recovery can be separated from the effect of the drug.
11. (5.2 − 8.0) ÷ 8.0 × 100 = −35%, a decrease of 35%.
12. A small group of healthy volunteers, to test safety and how the body handles the drug.

Where marks are usually lost

• Saying the hybridoma “makes monoclonal cells” or that the tumour cell makes the antibody.
• Describing a pregnancy test without naming hCG, or without saying why the control line is needed.
• Writing that monoclonal antibodies “cure” cancer. They are described as a potential treatment.
• Giving “kills bacteria” for every aseptic step without saying which object or surface is made sterile.
• Mixing up sterilising equipment (autoclave) and cleaning a surface (alcohol).
• Using the diameter instead of the radius, or forgetting to subtract the disc from a clear zone.
• Calling phase 1 a test of effectiveness when its main aim is safety.
• Omitting the comparison group: results from a drug group with no placebo or control cannot show the drug works.
• Leaving out units or the sign of a percentage change.

Official syllabus

OCR GCSE (9-1) Gateway Science Biology A (J247), Version 4.0 (August 2026), for first assessment in 2018, published by OCR. Statements B6.3m, B6.3n, B6.3p and B6.3q.