Cambridge IGCSE Biology 0610: Biotechnology and genetic modification – Study Guide

This study guide covers topic 21, Biotechnology and genetic modification, of the Cambridge IGCSE Biology 0610 syllabus for examination in 2026, 2027 and 2028. It works through syllabus sections 21.1, 21.2 and 21.3 in order. Core statements are examined on Papers 1–4; Supplement statements are examined only on the Extended papers (Papers 2 and 4), and they are labelled “Extended only” below.

For the whole course, see the Cambridge IGCSE Biology hub and the printable 0610 checklist. When you have worked through this page, move on to the topic 21 revision notes and the topic 21 practice questions.

What this unit covers

Syllabus section	What you must be able to do	Tier
21.1.1	State that bacteria are useful because they reproduce rapidly and can make complex molecules	Core
21.1.2	Discuss why bacteria are useful: few ethical concerns; presence of plasmids	Extended only
21.2.1–21.2.2	Describe the role of anaerobic respiration in yeast in making ethanol for biofuels and in bread-making	Core
21.2.3	Describe the use of pectinase in fruit juice production	Core
21.2.4	Investigate and describe the use of biological washing powders that contain enzymes	Core
21.2.5	Explain the use of lactase to produce lactose-free milk	Extended only
21.2.6	Describe how fermenters are used for large-scale production of insulin, penicillin and mycoprotein	Extended only
21.2.7	Describe and explain the conditions controlled in a fermenter: temperature, pH, oxygen, nutrient supply, waste products	Extended only
21.3.1	Describe genetic modification (GM)	Core
21.3.2	Outline four examples of GM	Core
21.3.3	Outline the process of GM using bacterial production of a human protein, steps (a)–(f)	Extended only
21.3.4	Discuss the advantages and disadvantages of GM crops, including soya, maize and rice	Extended only

21.1 Why bacteria are useful

Biotechnology is the use of living organisms, usually microorganisms, to make useful products. Genetic modification is one tool within it.

Core

Bacteria are useful in biotechnology and genetic modification for two reasons:

• Rapid reproduction rate. Under good conditions a population grows very quickly, so a large amount of product can be made in a short time.
• Ability to make complex molecules. Bacteria can make proteins and other complex molecules that are useful to humans.

Extended only

You must also be able to discuss why bacteria are useful, limited to two further points:

• Few ethical concerns. Growing and manipulating bacteria raises far fewer ethical objections than doing the same with animals.
• The presence of plasmids. Plasmids are small circular loops of DNA found in bacterial cells, separate from the main circular DNA. They can be cut open, have a gene inserted and be put back into bacteria. This makes them ideal for carrying a new gene into a bacterium (see 21.3).

For “discuss”, say why each feature helps, not just that bacteria have it.

21.2 Biotechnology

Yeast, biofuels and bread (Core)

Yeast is a single-celled fungus. When it respires anaerobically it breaks down sugar without using oxygen:

glucose → alcohol + carbon dioxide

Extended candidates also need the balanced equation from topic 12: C₆H₁₂O₆ → 2C₂H₅OH + 2CO₂.

Ethanol for biofuels. Plant material that contains sugar (or starch broken down to sugar) is fed to yeast in large tanks with no oxygen. The yeast respires anaerobically and produces ethanol (the alcohol). The ethanol is separated and used as a fuel. The role of anaerobic respiration is to make the ethanol.

Bread-making. Flour, water, sugar and yeast are mixed into dough and left in a warm place. The yeast respires anaerobically, producing carbon dioxide. The gas forms bubbles that are trapped in the dough, so the dough rises. During baking the heat kills the yeast and the small amount of alcohol evaporates. Here the useful product of anaerobic respiration is the carbon dioxide, not the alcohol.

Pectinase and fruit juice (Core)

Pectin is a substance in plant cell walls that helps hold neighbouring cells together. Pectinase is an enzyme that breaks down pectin. When pectinase is added to crushed fruit:

• cell walls break down, so more juice is released from the cells, giving a higher yield
• the juice is clearer, because less cloudy material is left suspended in it.

Worked example. Two 100 g samples of crushed pear were left for 15 minutes at 35 °C and then filtered. The sample without pectinase gave 18.0 cm³ of juice. The sample with pectinase gave 27.0 cm³. Calculate the percentage increase in juice volume.

increase = 27.0 − 18.0 = 9.0 cm³
percentage increase = (9.0 ÷ 18.0) × 100 = 50%

Answer: 50%. A good explanation would add that pectinase broke down pectin in the cell walls, so more juice could leave the cells.

Biological washing powders (Core, practical)

Biological washing powders contain enzymes that digest stains:

• proteases break down proteins (for example blood or egg) into amino acids
• lipases break down fats and oils into fatty acids and glycerol
• amylases break down starch into simpler sugars.

The products are small and soluble, so they dissolve in the wash water and are rinsed away. Because enzymes work at moderate temperatures, clothes can be washed at a lower temperature, which uses less energy. At high temperatures the enzymes are denatured and the powder works no better than a non-biological one.

The syllabus says investigate, so expect a planning or data question. A typical method:

1. Cut equal squares of cloth with the same size and type of stain (for example egg).
2. Put each square in the same volume and concentration of washing powder solution.
3. Keep each at a different temperature using water baths (the independent variable).
4. Record the time for the stain to disappear (the dependent variable).
5. Run a control with a non-biological powder, or with biological powder that has been boiled to denature the enzymes.
6. Repeat each temperature and calculate a mean.

Rate can be worked out as 1 ÷ time. Link any fall in rate at high temperature to denaturation of the enzyme, which changes the shape of the active site (topic 5).

Lactase and lactose-free milk (Extended only)

Lactose is the sugar in milk. Lactase is an enzyme that breaks lactose down into two simpler sugars, glucose and galactose. Some people do not produce enough lactase, so they cannot digest lactose properly. Adding lactase to milk breaks down the lactose before the milk is drunk, so these people can drink it.

Worked example. A sample of milk contains 48 g of lactose per dm³. Lactase breaks down 95% of it. Calculate the mass of lactose left per dm³.

lactose left = 5% of 48 = 0.05 × 48 = 2.4 g per dm³

Answer: 2.4 g per dm³.

Fermenters (Extended only)

A fermenter is a large vessel used to grow microorganisms in controlled conditions so that they make a useful product on a large scale. The syllabus names three products:

Product	Made by	Use
Insulin	Genetically modified bacteria	Treating diabetes
Penicillin	A fungus (the mould Penicillium)	An antibiotic
Mycoprotein	A fungus (Fusarium)	A high-protein meat substitute

The main features of a fermenter and why each is there:

Condition controlled	How	Why
Temperature	Water jacket with cold water flowing through; temperature probe	Respiration by the microorganisms releases heat. Too hot and enzymes denature; too cool and growth is slow
pH	pH probe; acid or alkali added	Enzymes work best at an optimum pH
Oxygen	Sterile air bubbled in; paddles (stirrer) mix it through	For aerobic respiration, which releases the energy needed for growth
Nutrient supply	Nutrients such as glucose and a nitrogen source added	Glucose for respiration; nitrogen to make amino acids and proteins for growth
Waste products	Gases leave through an outlet; product and waste removed	Wastes such as carbon dioxide can change the pH or become toxic and slow growth

The paddles also mix the contents so that microorganisms, nutrients and heat are spread evenly. The vessel is sterilised before use so that only the wanted microorganism grows.

Worked example. A cooling pump failed and the temperature in a fermenter rose from 28 °C to 34 °C in 3 hours. Calculate the mean rate of temperature rise and explain why the temperature rose.

rise = 34 − 28 = 6 °C
rate = 6 ÷ 3 = 2 °C per hour

Answer: 2 °C per hour. The microorganisms were still respiring, and respiration releases heat energy. With no cooling water, the heat was not removed.

21.3 Genetic modification

Core: what GM is

Genetic modification is changing the genetic material of an organism by removing, changing or inserting individual genes.

The syllabus lists four examples you must be able to outline:

1. Human genes into bacteria to make human proteins. For example, the human insulin gene is put into bacteria, which then make human insulin.
2. Genes into crop plants for herbicide resistance. The crop survives when the field is sprayed with a herbicide, so weeds die but the crop does not.
3. Genes into crop plants for resistance to insect pests. For example, maize given a gene from a bacterium so that its cells make a protein toxic to certain insect pests.
4. Genes into crop plants to improve nutritional qualities. For example, rice modified to make beta-carotene, which the body uses to make vitamin A.

Extended only: the process of GM

The syllabus limits you to six steps, using bacterial production of a human protein.

1. (a) The DNA making up the human gene is isolated by cutting it out with restriction enzymes. This leaves sticky ends: short single-stranded lengths of DNA.
2. (b) A bacterial plasmid is cut with the same restriction enzymes, which leaves complementary sticky ends.
3. (c) The human gene is inserted into the plasmid. The complementary sticky ends pair up and DNA ligase joins the DNA, forming a recombinant plasmid.
4. (d) Recombinant plasmids are inserted into bacteria. You do not need details of how.
5. (e) The bacteria containing recombinant plasmids multiply, for example in a fermenter.
6. (f) The bacteria express the human gene: they use it to make the human protein, which is then collected.

Extended only: GM crops, advantages and disadvantages

The syllabus names soya, maize and rice. “Discuss” means give both sides.

Advantages

• Herbicide-resistant soya: fields can be sprayed to kill weeds without killing the crop, so less competition and higher yields.
• Insect-resistant maize: less insecticide needs to be sprayed, which saves money and harms fewer other insects; less crop is lost to pests.
• Nutritionally improved rice: can reduce vitamin A deficiency where rice is the main food.

Disadvantages

• GM seed can be expensive, and farmers may have to buy new seed each year.
• Genes may transfer to wild relatives by pollination, possibly producing herbicide-resistant weeds.
• Heavy herbicide use kills weeds that other species rely on, which can reduce biodiversity.
• Insect pests may become resistant to the toxin over time.
• Some people are concerned about possible effects on human health, such as allergies, even though evidence is limited.
• Growing one variety over large areas reduces genetic variation in the crop.

Common errors

• Saying yeast in bread is useful because of alcohol. The useful product is carbon dioxide.
• Writing “pectinase breaks down cell membranes”. It breaks down pectin in cell walls.
• Giving “lactase breaks down lactose into glucose” without galactose.
• Saying fermenters need heating. They usually need cooling, because respiration releases heat.
• Writing “different restriction enzymes” or leaving out “same” when describing cutting the plasmid.
• Using “DNA ligase” to cut DNA. Restriction enzymes cut; ligase joins.
• Listing only advantages when a question says “discuss” GM crops.

Next steps

Test your recall with the topic 21 revision notes, then work through the topic 21 practice questions. To find gaps across the whole course, try the free 0610 Core diagnostic or the 0610 Extended diagnostic.

Official syllabus

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