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3.2.2
All Cells Arise From Other Cells
Analytical deep dive — question counts, mark distribution, mastery curves, command-word breakdowns, and examiner narrative analysis.
Questions
33
Total marks
71
Marks / Q
2.2
Accessibility
61.5%
Mastery
33.4%
Student strength
48.7%
01
At a glance
3.2.2 · All Cells Arise From Other Cells
8YRSYNTHESIS
3.2.2 (All Cells Arise From Other Cells) appeared in 8 of the 8 years between 2017 and 2024, contributing 33 questions and 71 marks across Papers 1, 2 and 3. APPLICATION dominates the mark distribution at 43.7% of total marks. The accessibility–mastery gap sits at 28.1 percentage points (61.5% vs 33.4%) — most students reach partial credit, but full marks remain harder to secure. The largest single question observed is worth 5 marks, signalling that AQA expects complete hierarchical accounts in this sub-section. Mastery varied year-to-year, lowest in 2025 (10.0%) and highest in 2022 (41.2%).
Access–mastery gap
+28 pp
Lowest mastery
2019 · 25.0%
Highest mastery
2022 · 41.2%
02
Question type split
By marks · compound to dominant
71MARKS
71
marks
Application43.7%31 marks
Knowledge40.8%29 marks
Calculation15.5%11 marks
(by marks; compound rows assigned to dominant type):
03
Credit terms — quick reference
Mark scheme tier-locked
23TERMS
Tier 1 · Always credit
chromatids
Tier 2 · Sometimes credit
standard formbinary fissionDNA replicationdaughter cellsrangeoverlapprophaseanaphasesteriledisinfectspindle fibrescells in mitosis
Reject · Never credit
mitosisviral replicationexperimental hypothesisno effect (vague)simple log values statedrange of B greater than ASD/SE overlappingsignificanceresults due to chancecontracted
04
Question patterns
Recurring formats & tariff structure
0PARAGRAPHS
05
Year-over-year presence
P1 + P3 · 2017–2024
8YEARS
| Year | Questions | Total marks | Mean accessibility | Mean mastery |
|---|---|---|---|---|
| 2017 | 5 | 10 | 56.0% | 33.4% |
| 2018 | 3 | 5 | 49.0% | 26.3% |
| 2019 | 1 | 2 | 55.0% | 25.0% |
| 2020 | 0 | 0 | — COVID | — COVID |
| 2021 | 2 | 7 | — COVID | — COVID |
| 2022 | 8 | 17 | 69.8% | 41.2% |
| 2023 | 9 | 17 | 57.9% | 33.9% |
| 2024 | 4 | 10 | 68.8% | 30.0% |
06
Mark scheme intelligence
2017–2024 mark scheme corpus
28TERMS
Tier 1 — frequently credited
| Term | Times credited | Years | Notes |
|---|---|---|---|
| chromatids | 3 | 2018, 2021, 2022 |
Tier 2 — sometimes credited
| Term | Times credited | Years | Notes |
|---|---|---|---|
| standard form | 2 | 2017, 2023 | |
| binary fission | 2 | 2017, 2025 | |
| DNA replication | 2 | 2017, 2019 | |
| daughter cells | 2 | 2017, 2022 | |
| range | 2 | 2017 | |
| overlap | 2 | 2017, 2023 | |
| prophase | 2 | 2018, 2021 | |
| anaphase | 2 | 2021, 2022 | |
| sterile | 2 | 2022, 2023 | |
| disinfect | 2 | 2022, 2023 | |
| spindle fibres | 2 | 2022, 2024 | |
| cells in mitosis | 2 | 2022, 2024 |
Commonly rejected language
| Term | Times rejected | Years | Why rejected |
|---|---|---|---|
| mitosis | 1 | 2017 | |
| viral replication | 1 | 2017 | |
| experimental hypothesis | 1 | 2017 | |
| no effect (vague) | 1 | 2017 | |
| simple log values stated | 1 | 2017 | |
| range of B greater than A | 1 | 2017 | |
| SD/SE overlapping | 1 | 2017 | |
| significance | 1 | 2017 | |
| results due to chance | 1 | 2017 | |
| contracted | 1 | 2018 | |
| chromosomes split | 1 | 2018 | |
| Figure 2 evidence | 1 | 2018 | |
| anaphase | 1 | 2018 | |
| telophase | 1 | 2018 | |
| interphase | 1 | 2018 |
Marks in this sub-section are typically awarded for precise terminology and correct application of biological principles. Sequential mark schemes — where each mark requires building on the previous one — are common in multi-mark questions; stating the first step without progression rarely earns more than one mark. Calculation marks are typically split between method (correct setup and value extraction) and answer (accurate numerical result), allowing partial credit when arithmetic errors occur.
07
Where students lose marks
Examiner-anchored error patterns
4CASE STUDIES
Conceptual errors
- Mitosis or meiosis events included in accounts of binary fission — binary fission does not involve a spindle, centromeres, or homologous chromosome pairing; students who wrote about spindle formation or chromosome condensation in a prokaryotic context scored zero even when the rest of the description was mechanistically plausible (2017 P1 Q04.1, 2022 P1 Q04.1)
- Meiosis events written for mitosis — crossing over and homologous chromosome separation appeared in descriptions of mitosis phases; the examiner noted this explicitly in 2024, where centromere splitting was also omitted and homologous pairs were described separating at anaphase (2024 P1 Q05.1)
- DNA replication described as part of mitosis rather than preceding it — AQA expects clear separation of S phase and mitosis; writing "DNA replicates during mitosis" was flagged as a misconception in 2019 and recurs across years (2019 P1 Q06.1)
- Viral replication assigned to binary fission or described as occurring inside the nucleus — a third of students scored zero on the 2022 viral replication question; mRNA injection into host cells and nuclear replication were both explicitly rejected; virus assembly before release was the most frequently missed mark point (2022 P1 Q04.1)
Vocabulary errors
- Standard form expressed with the decimal not after the first digit — 3.3 × 10⁻⁵ is correct; 33 × 10⁻⁶ or 0.33 × 10⁻⁴ are not; the convention was the barrier for a measurable fraction of students who arrived at the correct numerical result (2017 P1 Q02.4)
- "Bacteria became immune" to antibiotic — the correct term is resistance; immunity is an adaptive immune system concept and does not apply to prokaryotes; the examiner flagged this as the most common wrong-term error in 2023 (2023 P3 Q03.4)
- Null hypothesis written as an experimental prediction — students stated which treatment they expected to work rather than giving a neutral statement that the bacteriophage makes no difference to bacterial numbers in treated and untreated groups (2017 P3 Q02.3)
- Mitotic index multiplied by 100 — expressing it as a percentage rather than as a proportion; the formula gives a value between 0 and 1 and AQA does not accept percentage expression when the axis is labelled as a proportion (2024 P1 Q05.2)
Application errors
- Log scale treated as a linear axis — students read mean values of 8 bacteria cm⁻³ from a y-axis showing log(bacteria cm⁻³), losing the entire magnitude difference between treatment groups; the same pattern appeared in 2025 when students described phases without referencing the phase labels shown on the graph (2017 P3 Q02.4, 2025 P1 Q08.5)
- "Results are due to chance" used where "difference is due to chance" is required — a phrase error AQA penalises consistently; the statistical conclusion must specify that the difference between means is not significant, not that the results themselves arose by chance (2024 P1 Q05.3)
- Mitotic index trend described without biological interpretation — at ≥ 2 mm from the root tip, all cells are in interphase; most students described the decrease in mitotic index but did not identify the biological meaning — that all cells are in interphase — and the examiner explicitly noted that interphase as a cell-cycle phase was rarely recognised (2024 P1 Q05.4)
- Data described point-by-point rather than linked to binary fission or plasmid replication — students wrote "plasmid copy number increased" or "cloudiness plateaued" without connecting these observations to their cellular causes; earning zero when description is the only output is a consistent failure mode in application questions throughout this sub-section (2025 P1 Q08.5)
High-impact failures · examiner narrative
2018 P1 Q01.12 marks
Tested identification of evidence for mitosis from a figure. 62% of students failed to score at all; only 5.8% achieved both marks. The required format was evidence plus explanation — naming what is visible in the figure and explaining why that feature indicates mitosis — but students consistently gave one without the other: either a feature was named ("chromosomes visible") or an explanation was given ("cells are dividing") without the paired component. A compounding confusion was treating chromatids in a single chromosome as homologous pairs, which produced incorrect descriptions of the evidence. The low tariff (2 marks) makes the near-zero success rate particularly striking: every mark lost came from failing to complete a paired statement.
2022 P1 Q04.13 marks
Tested the viral replication mechanism. A third of students scored zero. Three errors concentrated the failure: attributing binary fission or mitosis to virus replication; claiming mRNA is injected into the host cell rather than viral nucleic acid; and stopping the account before virus assembly and release. Each error reflects a different category of confusion — binary fission conflates virus and prokaryote; the mRNA error inverts the replication sequence; failing to reach assembly reflects recall that terminates at nucleic acid replication. Students who described attachment protein binding to specific host receptors, rather than generic "attachment", scored more consistently.
2023 P3 Q03.22 marks
Tested calculation of bacterial numbers in undiluted culture from plate count data. 77% scored zero. The compound calculation required: calculating the mean count from plates, dividing by the plating volume, then multiplying by the dilution factor. Most students applied only one or two steps — typically calculating the mean and multiplying by 100,000 but omitting the volume correction. Students who obtained a partial answer also frequently failed to express the result in standard form. The 17% non-attempt rate on the subsequent logarithm question (Q03.3) traces directly from zero being carried forward here.
2024 P1 Q05.43 marks
Tested interpretation of mitotic index data across root positions from a figure. The key requirement — that a mitotic index of zero means all cells are in interphase, not simply that they are not dividing — was produced by very few. Most students described the trend accurately ("mitotic index decreases as distance increases") but framed it as "fewer cells doing the cell cycle" rather than recognising that all cells cycle and some are in mitosis while others are in interphase. The examiner explicitly noted that interphase as a cell-cycle phase was rarely recognised, despite being foundational to section 3.2.2.
08
Difficulty signals
Performance metric synthesis
28PP GAP
Mean accessibility
61.5%
Mean mastery
33.4%
Mean student strength
48.7%
The accessibility–mastery gap of 28.1 percentage points characterises this sub-section's difficulty profile. Most students reach partial credit; full marks remain harder to achieve. Within 3.2 (Cells), 3.2.2 ranks 3 of 4 sub-sections by mean mastery (1 = hardest). Mastery trajectory is broadly flat across the cohort window: 33.4% in 2017 → 10.0% in 2025 (-23.4 percentage points). Mean mastery was lowest in 2025 (10.0%) and highest in 2022 (41.2%).