Cloning and Biotechnology (6.2.1): OCR A Level Biology Exam Questions by Topic

OCRGenetics, Evolution and EcosystemsExam Questions
Written by Tom Whitburn

Cloning and biotechnology is a long spec point with a practical flavour. Spec point 6.2.1 asks you to describe natural clones in plants and animals, take a plant cutting, explain micropropagation, embryo twinning and somatic cell nuclear transfer (SCNT), and weigh up the arguments for and against cloning. It then turns to microorganisms: why they're used in biotechnology and food production, aseptic technique, batch and continuous fermentation, the standard growth curve, serial dilutions and immobilised enzymes.

The examiners' reports point to the same traps. Students describe micropropagation when the question asks for a cutting, write "electroporation" for SCNT, say "quick" or "cheap" without saying why, and talk about enzyme "shape" instead of the active site. The growth curve and serial dilution questions lose marks on a missing dilution factor, on answers not in standard form, and on mixing up the viable count with the total count.

Work through the eighteen questions below in order. They start with recall, move on to cloning, fermenters and enzymes in new contexts, and finish with aseptic technique, growth curves and dilution calculations. If you'd like to go through questions like these with me each week, my OCR A masterclasses run on Wednesdays at 5.15pm for Year 12 and on Tuesdays at 6.30pm or Thursdays at 5.15pm for Year 13.

Want help with this topic? It comes up in my weekly OCR A masterclasses. See the timetable →

What you need from GCSE

Each question on this page assumes you're secure on these GCSE ideas. If any of them feels shaky, look it up before you start.

  • Asexual reproduction involves only one parent and mitosis, so the offspring are genetically identical clones.
  • Gardeners clone plants by taking cuttings; tissue culture grows many plants from small groups of cells.
  • Embryo transplants and adult cell cloning (as used for Dolly the sheep) produce cloned animals.
  • Bacteria divide by binary fission; in good conditions their numbers double every generation.
  • Microorganisms are cultured on agar or in nutrient broth using sterilised equipment to prevent contamination.

Key terms

These words come up in the questions and mark schemes. Examiners expect you to use them exactly.

  • Vegetative propagation: natural asexual reproduction in plants from structures such as runners, bulbs, rhizomes, tubers and suckers, which grow from meristem tissue.
  • Micropropagation (tissue culture): growing many clones from a small explant of meristem tissue on sterile nutrient medium; the callus is divided and plant hormones trigger shoot and root growth.
  • Explant and callus: the small piece of tissue taken from the parent plant; the mass of undifferentiated cells it grows into.
  • Artificial embryo twinning: splitting an early embryo, whose cells are totipotent, into several parts, each implanted into a surrogate mother.
  • Somatic cell nuclear transfer (SCNT): the nucleus of a body cell is fused with an enucleated egg cell by an electric pulse (electrofusion); the embryo is implanted into a surrogate.
  • Batch and continuous fermentation: a fixed volume of medium grown for a set time (favours secondary metabolites) versus nutrients added and product removed all the time (faster growth, primary metabolites).
  • Aseptic technique: methods that stop unwanted microorganisms getting in, e.g. sterile equipment and medium, working near a Bunsen flame, flaming the neck of the flask.
  • Standard growth curve: lag, log (exponential), stationary and death (decline) phases of a population in a closed culture.
  • Serial dilution: diluting a culture step by step (e.g. 1 in 10 each time) so colonies can be counted, then multiplying back up by the dilution factor.
  • Immobilised enzyme: an enzyme held in place by adsorption, covalent bonding, entrapment in a matrix or membrane separation, so it can be reused and doesn't contaminate the product.

What these questions cover (OCR 6.2.1)

The questions test these learning outcomes from the OCR A Level Biology A specification (H420):

  • (a)(i) the production of natural clones for use in horticulture (natural clones in plants, e.g. runners, bulbs, tubers and rhizomes)
  • (a)(ii) how to take plant cuttings as an example of a simple cloning technique
  • (b)(i) the production of artificial clones of plants by micropropagation and tissue culture
  • (b)(ii) the arguments for and against artificial cloning in plants
  • (c) natural clones in animal species (e.g. twins formed by embryo splitting)
  • (d)(i) artificial clones in animals can be produced by artificial embryo twinning or by enucleation and somatic cell nuclear transfer (SCNT)
  • (d)(ii) the arguments for and against artificial cloning in animals
  • (e) the use of microorganisms in biotechnological processes
  • (f) the advantages and disadvantages of using microorganisms to make food for human consumption (bacterial and fungal sources)
  • (g)(i) how to culture microorganisms effectively, using aseptic techniques
  • (g)(ii) the importance of manipulating the growing conditions in batch and continuous fermentation in order to maximise the yield of product required
  • (h)(i) the standard growth curve of a microorganism in a closed culture (including N = N₀ × 2ⁿ)
  • (h)(ii) practical investigations into the factors affecting the growth of microorganisms (serial dilutions and broth (PAG7))
  • (i) the uses of immobilised enzymes in biotechnology and the different methods of immobilisation

How to use this page

Write your answer on paper before you open the mark scheme. Allow about 1.2 minutes per mark: the 18 questions are worth 43 marks, so about 52 minutes in total. Then mark your answer strictly against the mark scheme and read the examiners' tip underneath it. If you'd rather print the questions, download the PDF pack.

Recall

Question 1

A level Paper 3 · June 2024 · Q6(a) · 4 marks · Easy

Describe how artificial clones of plants are produced by micropropagation.

Question saying plants can be cloned and propagated in horticulture and agriculture, asking for a description of micropropagation for 4 marks.
Show the mark scheme Mark scheme: remove meristem tissue from a shoot tip or bud; use aseptic technique; place the explant on a culture medium with named nutrients; cells divide to form a callus; divide the callus; plant hormones such as auxins and cytokinins trigger shoot and root growth; transfer plantlets to compost.

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From the examiners' report: Most students scored well. Say where the meristem tissue comes from, such as a shoot tip, and give the job of each nutrient or hormone you name. Don't drift into taking cuttings.

Question 2

A level Paper 3 · June 2024 · Q6(c)(i) · 2 marks · Medium

Name structure X on a lily plant and outline how a gardener could make many clones from it.

Drawing of a lily plant with an underground structure X in the soil, and a peppermint plant with a horizontal stem Y growing along the soil surface.
Show the mark scheme Mark scheme: bulb (corm or tuber allowed); split or divide the bulb and plant each piece.

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From the examiners' report: Most named the bulb, but then replanted it whole or took a stem cutting. Say the bulb is divided first and each piece is planted. A gardener wouldn't use micropropagation.

Question 3

A level Paper 2 · June 2025 · Q17(c)(i) · 1 mark · Medium

State the property of embryo cells that makes cloning by embryo splitting possible.

Five-step procedure for cloning by embryo splitting: an egg is fertilised, the zygote divides into an embryo, the embryo is split, each smaller embryo is implanted into a surrogate mother and born normally.
Show the mark scheme Mark scheme: the cells are totipotent, able to differentiate into any cell type. "Undifferentiated" ignored.

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From the examiners' report: One word does it: totipotent. Don't give the wrong potency, and if you describe it, say the cells can become any type of cell.

Question 4

A level Paper 3 · June 2024 · Q1(c) · 2 marks · Easy

State two reasons, other than easy genetic modification, why E. coli suits biotechnology.

Question saying E. coli can be genetically modified to produce useful proteins and asking for two other reasons it is a suitable microorganism for biotechnology.
Show the mark scheme Mark scheme: short life cycle or fast growth; simple nutrient requirements; can be kept at relatively low temperatures; few ethical concerns; a qualified reason why it costs less.

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From the examiners' report: Short life cycle was the most common correct answer. Qualify anything vague: "cheap" needs a reason, such as needing only low temperatures.

Question 5

A level Paper 2 · June 2022 · Q21(a) · 2 marks · Medium

List two advantages, other than simple nutrient needs, of using microorganisms in food production.

Question saying microorganisms have simple nutrient requirements, which reduces costs, and asking for two other advantages of using microorganisms in food production.
Show the mark scheme Mark scheme: no welfare or ethical issues; easily genetically modified; rapid growth so production can meet demand; year-round production; take up little space; low costs because they work at low temperatures. First two answers marked.

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From the examiners' report: "Quick" and "cheap" on their own don't score. Say what is quick (rapid reproduction) or why it is cheap (works at low temperatures).

Question 6

A level Paper 3 · June 2019 · Q6(a)(ii) · 3 marks · Easy

Tick whether each statement applies to batch or continuous fermentation.

Table of five statements with batch and continuous columns: waste removed during fermentation; fixed volume of nutrient medium; secondary metabolites more likely; growth rate faster; culture grown for a fixed time.
Show the mark scheme Mark scheme: continuous for waste removed and faster growth rate; batch for fixed volume, secondary metabolites and fixed time. All five correct for 3 marks, four for 2, three for 1.

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From the examiners' report: Most scored 2 or 3. Secondary metabolites are made in batch fermentation, once growth slows, and growth is faster in continuous fermentation.

Question 7

A level Paper 2 · June 2023 · Q18(a) · 1 mark · Medium

State one method of immobilising enzymes other than adsorption, covalent bonding and entrapment.

Fig. 18.1 showing three methods of immobilising enzymes: adsorption onto a surface, covalent bonding to a carrier and entrapment in a matrix.
Show the mark scheme Mark scheme: membrane separation, encapsulation or microcapsules; a partially permeable membrane allowed.

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From the examiners' report: Only about a third scored. Learn membrane separation (encapsulation) as the fourth method; entrapment in beads and ionic bonding are just versions of what's shown.

Applying what you know

Question 8

A level Paper 2 · June 2019 · Q20(a)(i) · 4 marks · Hard

Describe how to clone a lavender plant by taking a cutting.

Question saying lavender is often cloned by taking cuttings, and that a farmer needs two cuttings from the same parent plant to test two fertilisers, asking how to take a cutting.
Show the mark scheme Mark scheme: use a healthy shoot; cut the stem at a slant between nodes; dip in rooting powder or hormone; plant in moist compost; cover with a plastic bag or remove some leaves to reduce transpiration.

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From the examiners' report: Answers about micropropagation scored nothing here. Describe a cutting step by step, starting with choosing a healthy shoot and cutting at a slant between nodes.

Question 9

A level Paper 2 · June 2019 · Q20(b) · 3 marks · Hard

Identify three advantages of vegetative propagation in agriculture.

Question saying cloning plants is also known as vegetative propagation and asking for three advantages in agriculture.
Show the mark scheme Mark scheme: some crops can't reproduce from seed; seedlings are less likely to survive; quicker than growing from seed; uniform, predictable size, quality or yield; easier to harvest; can be done at any time of year. "Many copies" ignored.

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From the examiners' report: Only a few scored. Improving a crop is selective breeding, not cloning. Link uniformity to a desirable quality, such as the same yield, and qualify "quick" (quicker than growing from seed).

Question 10

A level Paper 3 · June 2022 · Q4(b) · 3 marks · Medium

Evaluate the claim that both a sponge and a zebra shark produce clones when they reproduce asexually.

Description of asexual reproduction in a sponge (clumps of diploid cells detach and grow into new sponges) and a zebra shark (two haploid cells from meiosis fuse to form a diploid cell), with a student's claim that both produce clones.
Show the mark scheme Mark scheme: sponges produce genetically identical offspring; shark offspring are not clones; they have alleles from only the mother; crossing over and independent assortment in meiosis create new allele combinations.

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From the examiners' report: Deal with each animal in turn. For the shark, link meiosis to crossing over or independent assortment and say this gives genetic variation, not just "variation".

Question 11

A level Paper 2 · June 2019 · Q19(a)(i) · 2 marks · Medium

Describe stage A of cloning a frog by nuclear transfer and suggest a practical method for it.

Fig. 19.1: a nucleus from a donor tadpole's epithelial cell and an enucleated egg from an adult frog are combined at stage A, then develop through stages B to D into a cloned frog.
Show the mark scheme Mark scheme: the nucleus from the tadpole cell fuses with or enters the enucleated egg, using a needle, micropipette or electric pulse (electrofusion). Injection and electroporation ignored.

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From the examiners' report: Say where the nucleus comes from (the tadpole cell) and where it goes (the enucleated egg). The method is electrofusion or a micropipette; electroporation was the most common wrong answer.

Question 12

A level Paper 2 · June 2025 · Q17(d)(iii) · 1 mark · Medium

Suggest why cloned Przewalski's horses are healthier than Dolly the sheep was.

Information from earlier in this question:

Earlier part of the same exam question, giving the information this part uses. Question about Przewalski's horses cloned by SCNT to increase an endangered population, asking why their health is better than that of Dolly the sheep, the first mammal cloned by SCNT.
Show the mark scheme Mark scheme: developments in science, technology or knowledge; the DNA may have come from a younger cell.

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From the examiners' report: Most said the technique has improved since 1996. A sharper answer is that the donor nucleus may have come from a younger cell.

Question 13

A level Paper 2 · June 2022 · Q21(c)(ii) · 2 marks · Medium

Suggest and explain why a mycoprotein fermenter needs a cooling system.

Information from earlier in this question:

Earlier part of the same exam question, giving the information this part uses. Diagram of a continuous fermenter for mycoprotein: glucose and air, ammonia and carbon dioxide connections, a cold water cooling system and an outlet where product is collected.
Show the mark scheme Mark scheme: temperature affects growth rate or enzyme activity; the fungus's metabolic reactions (respiration) release heat; cooling inhibits pathogenic bacteria.

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From the examiners' report: Most got one mark. Say where the heat comes from, respiration by the fungus is exothermic, and then why that matters, enzymes would denature and growth would slow.

Question 14

A level Paper 2 · June 2023 · Q18(b) · 2 marks · Hard

Use the diagram to explain why immobilised enzymes may be less active than free enzymes.

Information from earlier in this question:

Earlier part of the same exam question, giving the information this part uses. Question saying immobilised enzymes can be reused but immobilisation can reduce activity, asking why with reference to the three methods in Fig. 18.1.
Show the mark scheme Mark scheme: covalent bonding, the matrix or carrier might change the shape of the active site; the active site might be hidden; the substrate must move through the matrix. "Enzymes can't move" and leakage ignored.

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From the examiners' report: Mention the active site every time: its shape could change, or it could be partly hidden by the carrier. "Enzyme shape" alone, or "the enzyme can't move", didn't score.

Practical and maths

Question 15

A level Paper 3 · June 2017 · Q2(b)(ii) · 2 marks · Medium

Describe two practical points that make sure a new yeast culture grows successfully.

Question about setting up an initial culture of the yeast Saccharomyces cerevisiae, asking for two practical considerations to make sure the population grows successfully.
Show the mark scheme Mark scheme: aseptic technique; provide nutrients or a respiratory substrate; a suitable temperature (15–35 °C); a buffer for pH; stirring. "Control" or "keep constant" temperature or pH ignored.

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From the examiners' report: Aseptic technique plus a suitable temperature or pH scores both marks. Say the temperature is optimum or suitable, not just "controlled", and never sterilise the culture itself.

Question 16

A level Paper 2 · June 2022 · Q17(d) · 4 marks · Hard

Explain, using the graph, the fall in viable bacteria between 40 h and 48 h.

Information from earlier in this question:

Earlier part of the same exam question, giving the information this part uses. Earlier part of the same exam question, giving the information this part uses. Earlier part of the same exam question, giving the information this part uses. Graph of the number of bacteria in a closed culture over 48 hours, showing the total count and the viable count; the viable count falls between 40 and 48 hours while the total count stays very high.
Show the mark scheme Mark scheme: reproduction rate lower than death rate; total count much higher than viable count, with figures and units; build-up of waste; less oxygen or nutrients; increased competition; dead cells reduce access to nutrients.

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From the examiners' report: Stick to 40–48 h: this is the death phase, so reproduction rate is lower than death rate as waste builds up and nutrients run out. Bacteria don't have a "birth rate", and the total count includes the dead cells.

Question 17

A level Paper 3 · November 2021 · Q2(d)(ii) · 3 marks · Medium

Use a log-scale growth curve to calculate the number of bacteria in 50 cm³ on day 1.

Information from earlier in this question:

Earlier part of the same exam question, giving the information this part uses. Fig. 2.3: growth curve of bacteria in a closed culture as log10 number of cells per cm³ over 20 days, with nitrate concentration on a second axis.
Show the mark scheme Mark scheme: read about 4.7 from the graph, 10^4.7 = 50 119 cells per cm³, × 50 = 2.5 × 10⁶ cells; values from 10^4.5 to 10^4.8 accepted; maximum 2 marks if not in standard form.

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From the examiners' report: Convert the log first: 10 to the power of the reading gives cells per cm³. Then multiply by 50 cm³ and give the answer in standard form.

Question 18

A level Paper 2 · June 2018 · Q19(b)(i) · 2 marks · Medium

Use colonies from a serial dilution to calculate the number of viable bacteria in a sample.

Information from earlier in this question:

Earlier part of the same exam question, giving the information this part uses. Serial dilution: 0.1 cm³ of culture in 9.9 cm³ water (Tube A), then 1 cm³ into 9 cm³ for Tubes B to F; 0.1 cm³ from each tube was cultured on agar and Fig. 19 shows the plates.
Show the mark scheme Mark scheme: 6.0 × 10⁷; maximum 1 mark if not in standard form; 6 × 10⁶ or 6 × 10⁸ get 1 mark.

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From the examiners' report: Fewer than 1 in 5 got both marks; many were out by a factor of 10 or 100. Write down the total dilution of Tube F before you multiply, and give the answer in standard form.

Where students lose marks (from OCR examiners' reports and mark schemes)

Each point below is followed by wording that gained marks.

  • A cutting is not micropropagation: Asked how to clone lavender by taking a cutting, many students described micropropagation and scored nothing.

    ✔ Gains credit: "Use a healthy shoot, cut the stem at a slant between nodes, dip in rooting powder and place in moist compost".

  • Divide the bulb before replanting: Most students named the bulb but replanted it whole or took a stem cutting instead.

    ✔ Gains credit: "Bulb; split / divide the bulb and plant".

  • Embryo cells split because they're totipotent: Some students named the wrong potency or wrote that the cells are "undifferentiated", which is ignored.

    ✔ Gains credit: "The cells are totipotent / able to differentiate into any cell type".

  • SCNT fuses a nucleus; it doesn't electroporate: Electroporation was the most common wrong answer for getting the tadpole nucleus into the egg, and many didn't say where the nucleus came from.

    ✔ Gains credit: "The nucleus from the tadpole cell fuses with the enucleated egg using an electric pulse / electrofusion / micropipette".

  • Secondary metabolites come from batch culture: Many students thought secondary metabolites are made in continuous fermentation and that growth is faster in batch fermentation.

    ✔ Gains credit: "Secondary metabolites are more likely to be produced: batch" and "the growth rate tends to be faster: continuous".

  • Immobilisation changes the active site: Many students said immobilisation changes the "enzyme shape" or "tertiary structure", or that the enzyme can't move, without mentioning the active site.

    ✔ Gains credit: "Covalent bonding / the carrier might affect the shape of the active site" and "the active site might be partly hidden".

  • Total count includes the dead cells: Explaining the decline phase, many students wrote about a "birth rate", described the whole curve from 0 h, or treated viable and total counts as two competing species.

    ✔ Gains credit: "Reproduction rate is lower than death rate" and "the total count is much higher than the viable count, so the culture is full of dead cells".

  • Multiply back by the dilution factor: Fewer than 1 in 5 students got both marks for the colony count; many were out by a factor of 10 or 100 or ignored the standard form instruction.

    ✔ Gains credit: "6.0 × 10⁷" viable bacteria, in standard form.

Download the questions

Download the PDF pack (18 questions, mark schemes at the end)

Keep practising

Questions, mark schemes and examiners' report extracts © OCR.

Tom Whitburn
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Manipulating Genomes (6.1.3): OCR A Level Biology Exam Questions by Topic