OCR A 6.1.1 · 14 written questions · 26 marks · about 30 minutes · marked as you go
This free quiz has 14 written exam questions on cellular control, all taken from OCR A Level Biology A papers (A level, 2017 to 2025, plus OCR practice or sample papers). Short answers mark themselves. For longer answers you write your answer, then tick off the OCR mark-scheme points you made, so you see exactly where the marks are. The quiz covers how mutations affect proteins and how cells control which genes are expressed, from the lac operon and transcription factors to mRNA editing, cAMP and the Hox genes that lay out a body plan. OCR has set fewer short-answer questions on this topic than on most, so this quiz is shorter than the others in the series.
What the quiz covers (OCR A spec 6.1.1)
Gene mutations (6.1.1(a)): how a substitution can introduce an early stop codon, how inserting a gene can affect other genes on the same chromosome, and why non-coding DNA varies more.
Transcriptional control (6.1.1(b)): the lac operon in E. coli, the promoter, and how a hormone-activated transcription factor controls transcription in eukaryotes.
Gene interaction at the molecular level (6.1.1(b)): suggesting how one allele's product can block the expression of another.
Post-transcriptional and post-translational control (6.1.1(b)): editing primary mRNA, removing introns, splicing, and activating proteins with cyclic AMP.
Body plans (6.1.1(c)): Hox and homeobox genes, why they are highly conserved, and why fruit flies are used to study them.
Apoptosis and body form (6.1.1(c)–(d)): how a failed Hox-controlled signal for apoptosis can leave fingers joined.
How to use it
Write every answer in full, as you would in the exam: the mark for each question is shown, so you know how much to write. When you self-mark, only tick a point if your answer clearly makes it, then read the examiner's tip under each question. Your progress is saved on your device, so you can do it in two sittings, and at the end you can retry just the questions where you dropped marks.
Prefer multiple choice? Try the 20-question Cellular Control and Manipulating Genomes multiple choice quiz first.
Open the Cellular Control quiz in a new tab (easier on a phone)
Where students lose marks (from OCR examiners' reports and mark schemes)
Each point below is followed by wording that gained marks.
Say what allele B produces: Writing that 'allele B turns off allele A'. OCR gave no credit for this, because an allele doesn't act directly on another allele.
✔ Gains credit: Allele B codes for a repressor protein (or transcription factor) that binds to the promoter of allele A, so A is not transcribed.
Translation stops, not transcription: Saying that a premature stop codon stops transcription, or naming the stop codon without saying what it does to the protein.
✔ Gains credit: The mutation introduces an early stop codon, so translation ends early and the polypeptide chain is shorter (truncated).
Substitutions don't shift the frame: Calling a single-base substitution a frameshift. OCR's mark scheme treats 'frameshift' as a contradiction for a substitution.
✔ Gains credit: A substitution changes one codon only; an insertion or deletion causes a frameshift, so every triplet downstream is different.
Introns leave mRNA, not DNA: Writing that introns are removed 'from DNA'. The DNA keeps its introns: they are cut out after transcription.
✔ Gains credit: Introns are removed from primary mRNA to produce mature mRNA.
Splice out introns, join exons: Mentioning only the removal of introns, or using 'splice' to mean 'remove'. Few students mentioned the exons being joined.
✔ Gains credit: Introns are spliced out of the primary transcript and the exons are joined together (spliced).
The lac operon is transcriptional: Using the lac operon or histone modification to answer a question about post-transcriptional control.
✔ Gains credit: Post-transcriptional control: editing primary mRNA, removing introns and joining exons (RNA editing and capping were also credited).
Say why DNA is non-coding: Describing what 'non-coding' means instead of explaining why some regions don't code for a polypeptide. 'Introns are non-coding' on its own was ignored.
✔ Gains credit: Introns are removed when primary mRNA is edited, so they are not in mature mRNA and are never translated; other regions are regulatory sequences.
'Regulatory' is too vague: Naming the genes that control body plan as 'regulatory genes' or the 'lac operon'.
✔ Gains credit: Hox genes (homeobox or homeotic genes).
Keep practising
Try the Cellular Control and Manipulating Genomes multiple choice quiz, the DNA and Protein Synthesis multiple choice quiz, the Nucleotides, DNA and Protein Synthesis written quiz or the Patterns of Inheritance written quiz, or browse all our OCR A Level Biology quizzes. Our OCR A masterclasses (Year 12 on Wednesdays at 5.15pm, Year 13 on Tuesdays at 6.30pm) work through real exam questions on one topic each week.
Questions, mark schemes and examiners' report extracts © OCR.