Cambridge O Level Biology 5090: Biotechnology and genetic modification (5090) – Practice Questions

These are original questions written for Marlbridge, for revision and practice on this content. They are not reproduced past-paper questions, and they do not replicate the exam’s exact structure, question count or mark tariffs – examination boards hold copyright in their own papers. Use these alongside the official past papers from your board or school.

These questions cover Topic 18, Biotechnology and genetic modification, of the Cambridge O Level Biology 5090 syllabus for examination in 2026, 2027 and 2028 (version 4): every learning outcome in sections 18.1 Biotechnology and 18.2 Genetic modification. The syllabus is not tiered, so every question applies to every candidate.

Revise first with the study guide and the revision notes. The course hub and the printable checklist list the other topics, and the free 10-minute diagnostics help you decide what to revise next. A calculator is useful for questions 3, 5, 7 and 10.

Questions

1. A baker leaves bread dough in a warm place for an hour. Explain why the volume of the dough increases. [3]

2. Describe what is meant by genetic modification. [2]

3. In ideal conditions, a species of bacterium divides into two every 20 minutes.

(a) Calculate how many cells are produced from one cell after 3 hours. Show your working. [2] (b) Explain why this feature makes bacteria useful in biotechnology. [1] (c) Discuss two other reasons why bacteria are useful in genetic modification. [4]

4. A company grows a fungus in a fermenter to make an antibiotic.

(a) Explain why the fermenter has a jacket through which cold water flows. [2] (b) During a run, the pH probe shows that the pH is falling. Suggest a cause and state how the problem is corrected. [2] (c) Sterile air is bubbled into the fermenter and paddles stir the contents. Explain why. [2] (d) State two other conditions, apart from temperature, pH and oxygen, that are controlled in a fermenter. [2]

5. A student made three identical balls of dough, put each in a measuring cylinder, and kept them at different temperatures. The height of each dough was 4.0 cm at the start. The table shows the heights after 40 minutes.

Temperature / °C	Height after 40 minutes / cm
20	5.2
35	8.8
60	4.0

(a) Calculate the mean rate of rise at 35 °C, in cm per minute. [2] (b) Explain why the dough rose more at 35 °C than at 20 °C. [2] (c) Explain the result at 60 °C. [2] (d) State two variables the student kept constant. [2]

6. A cloth stained with egg was washed with biological and non-biological washing powder at different temperatures. The table shows the percentage of the stain removed.

Temperature / °C	20	30	40	50	60
Biological / %	40	65	85	55	30
Non-biological / %	20	25	35	40	45

(a) State the difference between the two powders at 40 °C. [1] (b) Explain the results for the biological powder between 20 °C and 60 °C. [3] (c) Name the type of enzyme that removes the egg stain. [1] (d) Suggest one environmental advantage of using biological powder. [1]

7. 100 g of crushed plums gave 12 cm³ of juice in 15 minutes. The same mass of crushed plums treated with pectinase gave 21 cm³ in 15 minutes.

(a) Calculate the percentage increase in juice volume. [2] (b) Explain how pectinase increases the volume of juice. [2] (c) Describe a suitable control for this experiment. [1] (d) State one other benefit of using pectinase in juice production. [1]

8. Some milk is sold as lactose-free.

(a) Name the enzyme used to make lactose-free milk. [1] (b) Name the two products formed. [2] (c) State who benefits from drinking lactose-free milk. [1]

9. Human insulin is now made by bacteria.

(a) Outline how bacteria have been changed so that they make human insulin, and how large amounts are produced. [4] (b) Suggest why insulin made this way can supply large numbers of people with diabetes. [1]

10. A farmer grew a herbicide-resistant variety of maize in one field and a non-modified variety in a similar field. Both fields were sprayed in the same way to control weeds. The yields were 3.2 tonnes per hectare for the non-modified maize and 4.0 tonnes per hectare for the herbicide-resistant maize.

(a) Calculate the percentage increase in yield. [2] (b) Explain how herbicide resistance leads to a higher yield. [3] (c) Outline how genetic modification can make a crop more nutritious. [2]

11. Cotton plants have been genetically modified to resist insect pests. Discuss the potential advantages and risks of growing this cotton. [6]

Answers

1. Yeast respires anaerobically, using sugar in the dough [1]. Carbon dioxide is released [1]. The gas is trapped as bubbles in the dough, so the volume increases [1]. [3] Examiner insight: The gas must be named as carbon dioxide; “air”, “oxygen” or “alcohol” in its place gives an incorrect mechanism.

2. Changing the genetic material of an organism [1] by removing, changing or inserting individual genes [1]. [2] Examiner insight: Use the syllabus wording; “changing DNA” alone does not say how, so it describes only half of the definition.

3. (a) 3 hours = 180 minutes; 180 ÷ 20 = 9 divisions [1]; 2⁹ = 512 cells [1] (b) A large population, and so a large amount of product, is made in a short time [1]. (c) There are no ethical concerns over their manipulation and growth [1], so they can be changed and grown in large numbers without the objections raised by using animals [1]. They contain plasmids [1], so a gene can be inserted into a plasmid and taken up by the bacterium [1]. [7] Examiner insight: In (c), “discuss” means each reason needs its consequence; a bare list of “ethics, plasmids” states features but does not explain them.

4. (a) Respiration of the fungus releases heat [1]; cooling keeps the temperature at the optimum so enzymes are not denatured [1]. (b) Acidic waste products are building up [1]; alkali is added to raise the pH [1]. (c) Oxygen is needed for aerobic respiration, so the fungus grows and makes product [1]; stirring spreads oxygen and nutrients evenly through the mixture [1]. (d) Nutrient supply [1]; removal of waste products [1]. [8] Examiner insight: The syllabus limits fermenter conditions to five; answers such as “light” or “pressure” fall outside that list and are not the conditions asked about.

5. (a) Rise = 8.8 − 4.0 = 4.8 cm [1]; 4.8 ÷ 40 = 0.12 cm per minute [1] (b) At 35 °C the yeast enzymes are closer to their optimum, so they work faster [1]; anaerobic respiration is faster, so more carbon dioxide is released and trapped in the dough [1]. (c) The dough did not rise at all [1]; at 60 °C the yeast enzymes are denatured, so no respiration takes place and no carbon dioxide is made [1]. (d) Any two: mass of dough; mass of yeast; mass of sugar; time [1] [1]. [8] Examiner insight: For (a), subtract the starting height first; dividing 8.8 by 40 gives a rate that includes the dough’s original size.

6. (a) Biological removes 50 percentage points more stain (85% compared with 35%) [1]. (b) From 20 °C to 40 °C stain removal increases because the enzymes have more kinetic energy and work faster [1]; the optimum is about 40 °C, where 85% is removed [1]; above 40 °C removal falls, to 30% at 60 °C, because the enzymes are denatured [1]. (c) Protease [1]. (d) Clothes can be washed at a lower temperature, so less energy is used to heat the water [1]. [6] Examiner insight: In (b), quote values from the table with units, and use “denatured” rather than “killed” for the fall.

7. (a) Increase = 21 − 12 = 9 cm³ [1]; (9 ÷ 12) × 100 = 75% [1] (b) Pectinase breaks down pectin in the plant cell walls [1], so more juice is released from the cells [1]. (c) The same mass of crushed plums with boiled (denatured) pectinase added, kept for the same time at the same temperature [1]. (d) The juice is clearer [1]. [6] Examiner insight: A control needs the enzyme to be inactive while everything else stays the same; “no plums” or “a different fruit” changes more than one variable.

8. (a) Lactase [1] (b) Glucose [1] and galactose [1] (c) People who are lactose intolerant (cannot digest lactose) [1]. [4] Examiner insight: Check the spelling: lactose is the sugar and lactase is the enzyme; swapping them changes the meaning of the answer.

9. (a) The gene that controls the production of human insulin is cut from human DNA [1]. It is inserted into bacterial DNA, using a plasmid [1]. The bacteria are grown in a fermenter, where they reproduce rapidly [1], and the insulin they make is extracted and purified [1]. (b) Bacteria reproduce rapidly, so a very large amount of insulin can be made in a short time [1]. [5] Examiner insight: Name the gene precisely as the human insulin gene; “insulin is put into bacteria” confuses the protein with the gene that codes for it.

10. (a) Increase = 4.0 − 3.2 = 0.8 tonnes per hectare [1]; (0.8 ÷ 3.2) × 100 = 25% [1] (b) The herbicide kills the weeds but not the resistant maize [1]; there is less competition for light, water and mineral ions [1]; so the maize grows better and the yield is higher [1]. (c) A gene is inserted into the crop [1] so that it makes an additional vitamin, or a substance the body converts into one, for example Golden Rice making beta-carotene for vitamin A [1]. [7] Examiner insight: In (b), name what the weeds compete for; “the weeds are gone so the crop grows better” lacks the link to resources.

11. Advantages: less of the crop is damaged by insect pests, so yields are higher [1]; less insecticide needs to be sprayed, saving money [1]; fewer insects that are not pests are killed by sprayed insecticide [1]. Risks: the pests may evolve resistance to the toxin, so the benefit is lost [1]; insects that are not pests may be harmed if they feed on the cotton [1]; the inserted gene may spread to wild relatives by pollination [1]. Other valid points, such as the cost of buying seed each year, are also creditworthy. [6] Examiner insight: A “discuss” answer needs points on both sides; six advantages with no risks does not answer the question.

Where marks are usually lost

• Naming the gas that makes bread rise as oxygen or air instead of carbon dioxide.
• Giving the features of bacteria without the reason each one helps.
• Writing that a fermenter needs heating, when respiration means it usually needs cooling.
• Listing conditions outside the five in the syllabus.
• Calculating rates from the final height rather than from the change.
• Using “killed” for enzymes instead of “denatured”.
• Writing a control that changes more than one variable.
• Confusing lactose and lactase, or giving glucose as the only product.
• Saying insulin, rather than the insulin gene, is put into bacteria.
• Treating a “discuss” question as a list of advantages only.

Next steps

• Revision notes for this topic
• Study guide for this topic
• Enzymes practice questions
• Respiration practice questions
• Cambridge O Level Biology course hub
• Printable checklist
• All free 10-minute diagnostics
• Book a free trial class

Official syllabus

Cambridge O Level Biology 5090 syllabus for examination in 2026, 2027 and 2028 (version 4), Topic 18: Biotechnology and genetic modification, published by Cambridge Assessment International Education.