OxfordAQA International GCSE Biology: Reproduction, cell division, stem cells and tumours (9201) – 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 sections 3.5.1 and 3.5.2 of the OxfordAQA International GCSE Biology (9201) specification, Version 5.2, for exams May/June 2018 onwards. The qualification is untiered. Read the study guide and revision notes first. The course hub and checklist help you plan, and the free diagnostics show where to start.

Questions

1. A gardener grows new strawberry plants from runners. A runner is a shoot that grows from the parent plant and takes root.

(a) State the type of reproduction involved. [1] (b) The new plants are clones. Explain what this means. [1] (c) Explain why plants grown from runners show less genetic variation than plants grown from seeds made by pollination of two parent plants. [1]

2. A chimpanzee has 48 chromosomes in each body cell.

(a) State the number of pairs of chromosomes in a body cell. [1] (b) State the number of chromosomes in a sperm cell. [1] (c) Explain why a sperm cell has this number and not 48. [2]

3. A mouse has a gene for fur colour. One allele gives black fur and a different allele gives brown fur.

(a) Distinguish between a gene and an allele. [2] (b) A student writes: “Each chromosome carries one gene.” Correct this statement. [1] (c) State where in a cell chromosomes are found. [1]

4. A plant has 20 chromosomes in each body cell.

(a) Copy and complete the table for one cell dividing by each process. [3]

	Mitosis	Meiosis
Number of divisions
Number of cells made
Chromosomes in each new cell

(b) State the purpose of each process in the plant. [2]

5. A hiker cuts her hand. Over the next few days, the skin heals.

(a) Explain how mitosis helps the cut to heal. [2] (b) In a mature animal, cells that line the gut are replaced much more often than most other cells. Suggest why. [2]

6. A mouse body cell has 40 chromosomes. A fertilised mouse egg divides repeatedly by mitosis. Assume every cell divides at the same time in each round.

(a) Calculate the number of cells after 7 rounds of division. [1] (b) Calculate the smallest number of rounds needed for the number of cells to exceed 500. [2] (c) Calculate the total number of chromosomes in the embryo after 7 rounds and explain why each cell has 40. [2]

7. Cells differentiate as an organism develops.

(a) State what is meant by differentiation. [1] (b) A gardener cuts a shoot from a geranium and it grows roots. A limb cut from a mature animal does not grow a new animal. Explain the difference. [3] (c) Explain why the new geranium plant is genetically identical to the parent. [2]

8. A laboratory grows stem cells in a culture. The table shows the cell numbers.

Time in hours	0	20	40	60
Number of cells	500	1000	2000	4000

(a) Each cell divides at the same regular interval and none die. Calculate how many times each original cell line divided between 0 and 60 hours. [1] (b) Predict the number of cells at 100 hours. Show your working. [2] (c) Stem cells can come from an embryo made by therapeutic cloning to carry the patient’s genes. Explain why these stem cells are less likely to be rejected by the patient. [3] (d) Name one other source of stem cells that the specification mentions. [1]

9. A patient is paralysed after an accident. A panel must decide between two research treatments.

Treatment A uses stem cells from an embryo made by therapeutic cloning. The embryo is not allowed to develop. Treatment B uses stem cells from the bone marrow of a volunteer, who gives them in a medical procedure.

Make a judgement about which treatment the panel should support, using the information. Give points for and against each treatment. [6]

10. Tumours can form in the body.

(a) Distinguish between a benign tumour and a malignant tumour. [2] (b) A malignant tumour in the lung is followed by tumours in the liver. Explain how this can happen. [2] (c) Name one chemical carcinogen and one source of ionising radiation that can cause tumours. [2]

11. A doctor measures tumours in two patients over 6 months using scans.

	Diameter at start in mm	Diameter after 6 months in mm	Other findings
Patient P	12	21	Tumours found in liver
Patient Q	10	11	No tumours found elsewhere

(a) Calculate the percentage increase in diameter for Patient P. [2] (b) For each patient, calculate the mean growth in diameter per month, in mm. Give Patient Q’s answer to 2 decimal places. [2] (c) State which patient is more likely to have a malignant tumour, giving two reasons. [2] (d) In an illustrative data set, lung cancer cases per 100 000 people per year are 15 in non-smokers and 120 in heavy smokers. Calculate how many times greater the rate is in heavy smokers and suggest one reason from tobacco smoke for the difference. [2]

Answers

1. (a) Asexual reproduction [1]. (b) Each one has exactly the same genes as the parent and as every other runner plant [1]. (c) Runners involve one parent with no mixing of genetic information, whereas two parents give a mixture of genes [1]. [3] Examiner insight: The word “genetically” matters in part (b); “look the same” can fail because clones may differ in appearance through the environment.

2. (a) 48 ÷ 2 = 24 pairs [1]. (b) 48 ÷ 2 = 24 [1]. (c) Gametes are made by meiosis and have a single set of chromosomes [1]. At fertilisation the sperm and egg join, and the 24 plus 24 restores 48 [1]. [4] Examiner insight: Show the link to fertilisation; stating “half” without saying the full number is restored later is usually only part of the explanation.

3. (a) A gene is a section of genetic information that controls a characteristic [1]. An allele is a different form of the same gene, which may produce a different characteristic [1]. (b) Each chromosome carries a large number of genes [1]. (c) In the nucleus [1]. [4] Examiner insight: A definition of allele gains credit when it mentions a form of the same gene; “a type of gene” on its own is too loose.

4. (a) Mitosis: 1 division, 2 cells, 20 chromosomes [1]. Meiosis: 2 divisions, 4 cells [1], 10 chromosomes each [1]. (b) Mitosis: growth or replacement of body cells [1]. Meiosis: making gametes [1]. [5] Examiner insight: In table questions, write the actual numbers, such as 10, rather than “half”, because the question gives you the chromosome number to work from.

5. (a) Mitosis makes new cells [1] that are genetically identical to the damaged cells, replacing those lost [1]. (b) The gut lining is worn away or damaged by food and digestive enzymes [1], so cells must be replaced by division often [1]. [4] Examiner insight: Use a cause and an effect; just writing “they divide more” is a restatement of the question.

6. (a) 2⁷ = 128 cells [1]. (b) 2⁸ = 256 is not enough [1]; 2⁹ = 512 exceeds 500, so 9 rounds [1]. (c) 128 × 40 = 5120 chromosomes [1]. Each cell receives an identical copy of the genetic material before the cell divides [1]. [5] Examiner insight: Showing the check at 8 rounds makes it clear why 9 is the answer; a bare number can look like a guess.

7. (a) A cell becomes specialised for a particular job [1]. (b) Plant cells can still differentiate at any age [1], so cells in the cut shoot can become root cells [1]. Most animal cells specialise early, and a mature animal divides cells largely for repair and replacement [1]. (c) The new plant is produced from the parent by mitosis, which makes genetically identical cells [1]. There is no fusion of gametes or mixing of genetic information [1]. [6] Examiner insight: Comparisons gain more when both organisms are mentioned; describing only the plant leaves out half of the contrast.

8. (a) The number doubles every 20 hours, so 60 ÷ 20 = 3 divisions [1]. (b) 100 ÷ 20 = 5 doublings [1]; 500 × 2⁵ = 16 000 cells [1]. (c) The embryo carries the patient’s genes [1]. The stem cells are therefore genetically matched to the patient’s own cells [1], so the immune system does not treat them as foreign and attack them [1]. (d) Adult bone marrow [1]. [7] Examiner insight: Whenever a table is given, try the pattern on two intervals first; doubling in each row confirms the regular interval.

9. Treatment A, for: cells match the patient’s genes, so there is no rejection [1]. Treatment A, against: an embryo is used and not allowed to develop, which some people regard as destroying a human life [1]. Treatment B, for: bone marrow cells come from an adult, so no embryo is used [1]. Treatment B, against: cells from a volunteer may not match the patient, and the donor must go through a procedure [1]. A clear judgement is stated [1], supported by a reason that follows from the points, for example weighing the benefit of treating paralysis against the concerns about the embryo or the donor [1]. [6] Examiner insight: Judgement questions reward a balance of points on both treatments followed by a conclusion that follows from them; either choice can be justified.

10. (a) A benign tumour does not invade other tissues [1]; a malignant tumour has cells that invade healthy tissue [1]. (b) Some cells from the malignant tumour enter the bloodstream [1] and are carried to the liver, where they form secondary tumours [1]. (c) Chemical carcinogen: for example tobacco smoke or asbestos [1]. Ionising radiation: for example UV or X-rays [1]. [6] Examiner insight: “Spreads” alone is vague; name the route, which is the bloodstream, and the result, which is secondary tumours.

11. (a) Increase = 21 − 12 = 9 mm [1]. 9 ÷ 12 × 100 = 75% [1]. (b) Patient P: 9 ÷ 6 = 1.5 mm per month [1]. Patient Q: 1 ÷ 6 = 0.17 mm per month [1]. (c) Patient P [1]. The tumour grew faster and tumours were found in the liver, which suggests that cells have spread and formed secondary tumours [1]. (d) 120 ÷ 15 = 8 times greater [1]. Tobacco smoke contains chemical carcinogens that can cause cells to divide in an uncontrolled way [1]. [8] Examiner insight: Take the original value as the denominator in percentage change; using the final value is a common slip. Say what the figures show in words.

Where marks are usually lost

• Writing “the cell splits into two” for meiosis, which makes four gametes, not two.
• Saying chromosomes “split in half” instead of stating the number of chromosomes in each cell.
• Using “gene” and “allele” as if they mean the same thing.
• Not saying that clones are genetically identical, which is the key idea.
• Giving the percentage change as a fraction of the final value instead of the starting value.
• Explaining rejection without saying the cells have the patient’s genes.
• Listing only advantages or only objections in an ethics question.
• Describing a tumour as “cancer” without saying whether it invades other tissues.
• Leaving out units, such as mm per month, in rate answers.

Next steps

• Review the revision notes.
• Re-read the study guide.
• Visit the course hub and the checklist.
• Try all free 10-minute diagnostics.
• Next, book a free trial class.

Official syllabus

OxfordAQA International GCSE Biology (9201), specification Version 5.2, for exams May/June 2018 onwards, published by OxfordAQA. Sections 3.5.1 a and 3.5.2 a to o.