Cambridge IGCSE Biology 0610: Biotechnology and genetic modification – Revision Notes

These revision notes condense topic 21, Biotechnology and genetic modification, of the Cambridge IGCSE Biology 0610 syllabus for examination in 2026, 2027 and 2028. They cover syllabus sections 21.1–21.3. Core content is tested on Papers 1–4; Supplement content, marked “Extended only”, is tested only on Papers 2 and 4. For full explanations and worked examples, use the topic 21 study guide.

Also useful: the Cambridge IGCSE Biology hub, the printable 0610 checklist and the topic 21 practice questions.

Tier map at a glance

• Core (all papers): 21.1.1 why bacteria are useful; 21.2.1–21.2.4 yeast in biofuels and bread, pectinase, biological washing powders; 21.3.1–21.3.2 what GM is and four examples.
• Extended only (Papers 2 and 4): 21.1.2 ethics and plasmids; 21.2.5–21.2.7 lactase, fermenters and fermenter conditions; 21.3.3–21.3.4 the six-step GM process and GM crop advantages and disadvantages.

If you are sitting the Core papers, you still need every Core line here in full. If you are sitting Extended, the Core lines are examined as well.

Key definitions

Term	Meaning
Biotechnology	Using living organisms, usually microorganisms, to make useful products
Genetic modification	Changing the genetic material of an organism by removing, changing or inserting individual genes
Plasmid	Small circular loop of DNA in a bacterial cell, separate from the main circular DNA
Restriction enzyme	Enzyme that cuts DNA at a particular point, leaving sticky ends
Sticky ends	Short single-stranded lengths of DNA left after cutting with restriction enzymes
DNA ligase	Enzyme that joins pieces of DNA together
Recombinant plasmid	Plasmid containing DNA from another organism (here, a human gene)
Fermenter	Vessel used to grow microorganisms in controlled conditions on a large scale

21.1 Why bacteria are useful

Core — two reasons:

• rapid reproduction rate
• ability to make complex molecules.

Extended only — discuss, limited to:

• few ethical concerns over their manipulation and growth
• presence of plasmids, which can carry an inserted gene into bacteria.

21.2 Biotechnology

Summary table

Process	Organism or enzyme	What it does	Useful result	Tier
Biofuel	Yeast, anaerobic respiration	glucose → alcohol + carbon dioxide	Ethanol used as fuel	Core
Bread	Yeast, anaerobic respiration	Same reaction	Carbon dioxide bubbles make dough rise	Core
Fruit juice	Pectinase	Breaks down pectin in cell walls	More juice; clearer juice	Core
Washing powder	Proteases, lipases, amylases	Digest stains to small soluble molecules	Stains removed at lower temperature	Core
Lactose-free milk	Lactase	lactose → glucose + galactose	Milk for people who cannot digest lactose	Extended only
Fermenter	Bacteria and fungi	Large-scale growth	Insulin, penicillin, mycoprotein	Extended only

Balanced equation for yeast (Extended only, from topic 12): C₆H₁₂O₆ → 2C₂H₅OH + 2CO₂.

Method in steps: washing powder investigation (Core)

1. Equal-sized cloth squares, same stain, same amount.
2. Same volume and concentration of powder solution.
3. Change one variable only (for example temperature, using water baths).
4. Measure time for the stain to disappear; rate = 1 ÷ time.
5. Control: boiled biological powder or non-biological powder.
6. Repeat and take a mean.

Method in steps: yeast questions (Core)

1. Say the yeast respires anaerobically (without oxygen).
2. Give the word equation: glucose → alcohol + carbon dioxide.
3. Name the product that matters for the process in the question.
4. Bread: carbon dioxide bubbles are trapped, so dough rises; baking kills the yeast and the alcohol evaporates.
5. Biofuel: sugar from plant material is broken down; the ethanol is separated and burned as fuel.

Method in steps: any enzyme-in-industry answer

Use the same four-part pattern for pectinase, the washing powder enzymes and lactase:

1. Enzyme — name it.
2. Substrate — say what it breaks down (pectin; proteins, fats or starch; lactose).
3. Products — say what is formed where the syllabus expects it (glucose and galactose for lactase).
4. Benefit — say why this is useful (more and clearer juice; stains removed at lower temperatures; milk people can digest).

Where temperature is involved, finish with enzyme ideas from topic 5: rate rises towards the optimum, then falls because the enzyme is denatured and the active site changes shape.

Fermenter conditions (Extended only)

Condition	Controlled by	Reason
Temperature	Cooling water jacket, probe	Respiration releases heat; keep enzymes near optimum, avoid denaturing
pH	Probe, add acid or alkali	Keep enzymes at optimum pH
Oxygen	Sterile air in, paddles mix	Aerobic respiration for energy for growth
Nutrient supply	Add glucose and nitrogen source	Respiration; making proteins for growth
Waste products	Gas outlet; remove wastes	Wastes can alter pH or be toxic

Products to name: insulin (GM bacteria), penicillin (fungus), mycoprotein (fungus).

21.3 Genetic modification

Four Core examples

1. Human genes into bacteria → human proteins (such as insulin).
2. Genes into crop plants → herbicide resistance.
3. Genes into crop plants → resistance to insect pests.
4. Genes into crop plants → improved nutritional qualities.

Method in steps: making a human protein (Extended only)

1. Isolate the human gene using restriction enzymes → sticky ends.
2. Cut the plasmid with the same restriction enzymes → complementary sticky ends.
3. Insert the gene into the plasmid; DNA ligase joins it → recombinant plasmid.
4. Insert recombinant plasmids into bacteria (no detail needed).
5. Bacteria multiply.
6. Bacteria express the human gene → human protein.

GM crops: advantages and disadvantages (Extended only)

Advantages	Disadvantages
Higher yields	GM seed is costly; may need buying each year
Less insecticide sprayed (insect-resistant maize)	Genes may spread to wild relatives
Weeds killed without harming crop (herbicide-resistant soya)	Loss of weeds and insects reduces biodiversity
Better nutrition (vitamin A precursor in rice)	Pests may evolve resistance
More food from the same land	Health concerns raised by some people; less genetic variation in crops

How to answer “discuss GM crops”

1. Name the crop and the gene’s purpose (for example insect-resistant maize).
2. Give an advantage and link it to that purpose.
3. Give a disadvantage, again linked where possible.
4. Repeat until the marks are covered, keeping both sides roughly balanced.

A list of advantages alone cannot reach full marks, however long it is.

Must-know distinctions

• Bread vs biofuel: same reaction; bread needs the carbon dioxide, biofuel needs the ethanol.
• Restriction enzyme vs DNA ligase: restriction enzymes cut; ligase joins.
• Plasmid vs circular DNA: both are in bacteria; the plasmid is the small extra loop used in GM.
• Pectin vs pectinase: pectin is the substance in plant cell walls; pectinase is the enzyme that breaks it down.
• Lactase vs lactose: lactase is the enzyme; lactose is the sugar.
• Heating vs cooling a fermenter: respiration makes heat, so fermenters are mainly cooled.

Small worked reminders

• Percentage change = (new − old) ÷ old × 100. Insecticide use falling from 40 kg to 30 kg is (30 − 40) ÷ 40 × 100 = −25%, a 25% decrease.
• Mean rate = change ÷ time. Dough rising from 200 cm³ to 300 cm³ in 50 minutes rises at 100 ÷ 50 = 2 cm³ per minute.

Links to other topics

• Topic 2 — bacterial cell structure: cell wall, cell membrane, cytoplasm, ribosomes, circular DNA and plasmids.
• Topic 5 — enzyme action, active site, optimum temperature and pH, denaturation.
• Topic 12 — anaerobic respiration in yeast, including the balanced equation for Extended.
• Topic 17 — genes as lengths of DNA that code for proteins, which is why an inserted gene leads to a new protein.

Quick self-test

1. State two features of bacteria that make them useful in biotechnology. (Core)
2. Name the gas that makes bread dough rise.
3. State the word equation for anaerobic respiration in yeast.
4. What does pectinase break down, and where is that substance found?
5. Give one advantage of washing clothes at a lower temperature with a biological powder.
6. Name the products formed when lactase acts on lactose. (Extended)
7. Name a fungus product made in a fermenter. (Extended)
8. Why is cold water passed through the jacket of a fermenter? (Extended)
9. Which enzyme joins the human gene into the plasmid? (Extended)
10. Why must the plasmid be cut with the same restriction enzyme as the human gene? (Extended)
11. Give one disadvantage of growing herbicide-resistant crops. (Extended)
12. The mass of juice from crushed apples rose from 60 g to 75 g when pectinase was added. Calculate the percentage increase.

Answers

1. Rapid reproduction rate; ability to make complex molecules.
2. Carbon dioxide.
3. glucose → alcohol + carbon dioxide.
4. Pectin, found in plant cell walls.
5. Uses less energy (enzymes work at moderate temperatures and would be denatured if too hot).
6. Glucose and galactose.
7. Penicillin or mycoprotein.
8. Respiration of the microorganisms releases heat; cooling stops enzymes denaturing.
9. DNA ligase.
10. So the sticky ends are complementary and can pair up.
11. Genes may spread to wild relatives, producing herbicide-resistant weeds (or: reduced biodiversity).
12. (75 − 60) ÷ 60 × 100 = 25%.

Where marks are usually lost

• Stating the bread product as alcohol instead of carbon dioxide.
• Writing that pectinase breaks down cell membranes rather than pectin in cell walls.
• Giving only glucose as the product of lactase; galactose is needed too.
• Describing fermenter temperature control as heating instead of cooling.
• Missing “same” restriction enzymes, or saying ligase cuts DNA.
• Leaving out “sticky ends” or “recombinant plasmid” when the process is asked for.
• Giving only one side when asked to discuss GM crops.
• Forgetting a control (boiled or non-biological powder) in a washing powder plan.
• Quoting a percentage change with the old and new values swapped in the denominator.

Official syllabus

Cambridge IGCSE Biology 0610 syllabus for examination in 2026, 2027 and 2028 (Version 3), published by Cambridge University Press & Assessment (Cambridge International).