IB Biology D2.2 Gene expression: practice questions

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D2.2-01 · Paper 1A style · multiple choice · 1 mark · HL

Methylated promoter

What is the effect of methylating cytosine bases in the promoter of a gene? [1]

1. The base sequence of the gene is changed.
2. The mRNA of the gene is broken down more slowly.
3. RNA polymerase binds more strongly to the promoter.
4. Transcription of the gene is repressed.

Show the answer and the reasoning

Answer: D. D is correct. Methyl groups on promoter cytosines block the binding of transcription factors and RNA polymerase, so the gene is switched off. A is wrong because methylation is an epigenetic tag: the bases themselves are unchanged. B confuses this with control of mRNA degradation, which happens after transcription. C is the opposite of the real effect.

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The 4 questions in D2.2

1. D2.2-01 Methylated promoterPaper 1A style · multiple choice · 1 mark · HL
2. D2.2-02 Hybrids that differ in sizePaper 1A style · multiple choice · 1 mark · HL
3. D2.2-03 Stopping protein productionPaper 1A style · multiple choice · 1 mark · HL
4. D2.2-04 Twins drift apart epigeneticallyPaper 2 style · short answer · 7 marks · HL

More of D Continuity and change

• D1.1 DNA replication
• D1.2 Protein synthesis
• D1.3 Mutation and gene editing
• D2.1 Cell and nuclear division
• D2.3 Water potential
• D3.1 Reproduction
• D3.2 Inheritance
• D3.3 Homeostasis
• D4.1 Natural selection
• D4.2 Stability and change
• D4.3 Climate change

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Every Biology and Chemistry question here is original, written for practice in the style of the papers set since the 2025 syllabus, with invented data. Developed independently from the International Baccalaureate Organization, which has not endorsed it. Found a mistake? Email vytis@limeadmissions.com with the question id.