AQA GCSE Biology 8461: Cell division – 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 section 4.1.2 Cell division (4.1.2.1 Chromosomes, 4.1.2.2 Mitosis and the cell cycle, 4.1.2.3 Stem cells) of the AQA GCSE Biology (8461) specification, for teaching from September 2016 and exams from 2018 onwards. The content is assessed on Paper 1, set at Foundation and Higher Tier. No statement in 4.1.2 is marked (HT only), so every question here suits both tiers. A calculator is useful for questions 5, 6 and 7.

Learn the content first in the Cell division study guide and the revision notes. For questions on the whole of Topic 1, use the Cell biology practice questions; the questions below are different from those. The course hub is AQA GCSE Biology, and the printable checklist lists every point.

Questions

1.

(a) Write these structures in order of size, starting with the largest: gene, nucleus, chromosome. [1] (b) State what chromosomes are made of. [1] (c) State how chromosomes are normally arranged in body cells. [1]

2. For each situation, state whether the cells are dividing by mitosis, and give a reason.

(a) Cells in the skin around a cut dividing to close the wound. [1] (b) Cells in the testes dividing to produce sperm. [1] (c) A bacterial cell dividing into two. [1]

3. These events happen during the cell cycle. They are not in order.

• A – the nucleus divides
• B – the DNA replicates
• C – the cytoplasm and cell membrane divide
• D – the number of mitochondria increases
• E – one set of chromosomes is pulled to each end of the cell

(a) Put the events in the correct order. [2] (b) Explain why event B must happen before the cell divides. [2]

4. A scientist measures the mass of DNA in one cell over 14 hours, following the cell through its cycle.

Time (hours)	0	2	4	6	8	10	12	14
DNA per cell (arbitrary units)	6	6	8	10	12	12	6	6

(a) Give the time period during which DNA replication takes place. [1] (b) Give the time period during which mitosis most likely takes place. [1] (c) Describe what happens to the cell between 10 and 12 hours. [1] (d) Explain why the DNA per cell at 12 hours is exactly half the value at 10 hours. [2]

5. A student looks at a stained root tip under a microscope. In one field of view she counts 250 cells. In 15 of them, the chromosomes are visible and being pulled apart.

(a) Calculate the percentage of cells in mitosis. [2] (b) The full cell cycle in this tissue takes 25 hours. Estimate the time a cell spends in mitosis. Give your answer in minutes. [2] (c) Suggest why she should count cells in several fields of view, not just one. [1]

6. The student repeats the count in two regions of the same root. She counts 300 cells in each region.

Region	Cells in mitosis
Within 2 mm of the root tip	42
2 cm back from the tip	3

(a) Calculate the percentage of cells in mitosis in each region. [2] (b) Explain the difference between the two regions. [2]

7. A laboratory grows adult stem cells in a culture. It starts with 5000 cells. Each cell divides by mitosis every 20 hours.

(a) Calculate the number of cells after 100 hours, assuming all cells keep dividing. [3] (b) Give the reason all the cells in the culture are genetically identical. [1]

8. Plants contain meristem tissue.

(a) State where meristem tissue is found in a plant. [1] (b) Describe the function of the stem cells in meristems. [2] (c) A seed company has bred a variety of wheat that is resistant to a fungal disease. Explain why the company might use meristem tissue to produce plants to sell to farmers. [3] (d) Suggest one disadvantage to a farmer of growing only these cloned plants. [1]

9. An insect species has 8 chromosomes in each body cell.

(a) How many pairs of chromosomes is this? [1] (b) How many copies of each chromosome are there at the end of the first stage of the cell cycle? [1] (c) How many chromosomes are in each cell produced by mitosis? [1] (d) Explain why mitosis keeps the chromosome number the same. [2]

10. Doctors are researching stem cell treatment for people whose pancreas cannot make insulin.

(a) Suggest what the stem cells would need to differentiate into. [1] (b) Evaluate the use of embryonic stem cells produced by therapeutic cloning for this treatment. [6]

11.

(a) Describe how a fertilised egg develops into an embryo containing many different types of cell. [4] (b) Explain why cell division in an adult human is mainly for repair and replacement, while a tree can keep growing new shoots and roots throughout its life. [3]

Answers

1. (a) nucleus, chromosome, gene [1] (b) DNA (molecules) [1] (c) In pairs [1] Examiner insight: “Genes are made of chromosomes” reverses the relationship; the order mark needs all three in the right sequence.

2. (a) Yes – new, genetically identical skin cells replace damaged cells [1] (b) No – sperm are gametes, which are made by meiosis, not mitosis [1] (c) No – bacteria have no nucleus and divide by binary fission [1] Examiner insight: Each mark needs the decision and the reason together; “yes” or “no” alone scores nothing.

3. (a) D and B first (either order) [1]; then E, A, C [1] (b) So that there are two copies of each chromosome [1]; and each new cell receives a full, identical set of genetic material [1] Examiner insight: Allow D and B in either order, as both happen in the first stage; E must come before C.

4. (a) 2 to 8 hours [1] (b) Between 8 and 10 hours (DNA has finished doubling and the cell has not yet split) [1] (c) The cytoplasm and cell membrane divide, forming two new cells [1] (d) The DNA was doubled by replication before division [1]; then divided equally between the two identical new cells [1] Examiner insight: Time periods must be read from the table; a single time such as “4 hours” does not earn the mark for a period.

5. (a) 15 ÷ 250 × 100 [1] = 6% [1] (b) 0.06 × 25 = 1.5 hours [1]; 1.5 × 60 = 90 minutes [1] (c) One field may not be representative, so several give a more reliable (repeatable) estimate [1] Examiner insight: An answer left as 1.5 hours loses the final mark when minutes are asked for; allow ECF from an incorrect percentage in (a).

6. (a) Tip: 42 ÷ 300 × 100 = 14% [1]; 2 cm back: 3 ÷ 300 × 100 = 1% [1] (b) The tip contains meristem tissue, where cells divide rapidly by mitosis for growth [1]; further back, most cells have differentiated (become specialised), so few divide [1] Examiner insight: “Fewer cells divide further back” only restates the data; the explanation marks need meristem/growth and differentiation.

7. (a) Number of divisions = 100 ÷ 20 = 5 [1]; 5000 × 2⁵ [1] = 160 000 cells [1] (b) All the cells are produced by mitosis (from the same starting cells) [1] Examiner insight: Multiplying 5000 by 2 × 5 (to get 50 000) shows no doubling and earns only the first mark.

8. (a) At the growing tips of shoots and roots [1] (b) They can differentiate into any type of plant cell [1]; throughout the life of the plant, allowing growth [1] (c) Clones can be produced quickly and economically [1]; giving large numbers of plants [1]; all genetically identical, so all have the disease resistance [1] (d) All the plants are genetically identical, so a new disease that they cannot resist could affect the whole crop [1] Examiner insight: For (c), “it is cheaper” alone earns one mark; the third mark needs the link between identical genes and keeping the resistance.

9. (a) 4 pairs [1] (b) Two copies [1] (c) 8 [1] (d) The DNA replicates first, so there are two copies of each chromosome [1]; one set is pulled to each end of the cell, so each new cell gets one full set [1] Examiner insight: An answer of 4 for (c) confuses mitosis with meiosis and scores zero for that part.

10. (a) (Pancreas) cells that produce insulin [1] (b) Marking points (AQA marks 6-mark evaluate questions by levels; a top answer covers both sides and concludes):

• the embryo is produced with the same genes as the patient, so the cells are not rejected [1]
• embryonic stem cells can differentiate into most types of human cell, so they can form the needed cells [1]
• the treatment may help a condition that would otherwise need lifelong management [1]
• risk: viral infection could be transferred to the patient [1]
• some people have ethical or religious objections to producing and using embryos [1]
• a conclusion that weighs these points and is justified by them [1] Examiner insight: An answer that gives only benefits, or only objections, cannot reach the top level, however many points it lists.

11. (a) The fertilised egg divides by mitosis [1]; repeatedly, so the number of cells increases [1]; the cells are (embryonic) stem cells, which differentiate as the embryo develops [1]; differentiated cells gain different sub-cellular structures to become specialised cells [1] (b) Most animal cells differentiate at an early stage and lose the ability to form other cells [1]; trees have meristems at their shoot and root tips [1]; meristem cells can differentiate into any type of plant cell throughout the plant’s life [1] Examiner insight: “Plants have stem cells” without naming meristems or their position earns at most one of the three marks in (b).

Where marks are usually lost

• Putting DNA replication inside mitosis rather than in the first stage of the cycle.
• Writing “the cell divides” when the mark is for “the nucleus divides”.
• Giving a yes/no for mitosis in a context without a reason.
• Treating doubling as multiplication by the number of cycles (2 × n instead of 2ⁿ).
• Leaving time in hours when the question asks for minutes.
• Restating data (“more cells divide at the tip”) instead of explaining it with meristems and differentiation.
• Saying cells from mitosis have half the chromosomes.
• Evaluate answers that list one side only or give no conclusion.
• Writing that stem cells “cure” diabetes rather than “may help”.

Next steps

• Cell division revision notes
• Cell division study guide
• Cell biology practice questions
• AQA GCSE Biology course hub
• Printable AQA GCSE Biology checklist
• All free 10-minute diagnostics
• Book a free trial class

Official syllabus

AQA GCSE Biology (8461) specification, Version 1.0, for teaching from September 2016 and exams from 2018 onwards (AQA), section 4.1.2 Cell division (4.1.2.1 to 4.1.2.3).