Biology  by Bradford
IB Biology 2025 · Theme D · Continuity and change

D2.2 Gene expression. Practice questions with markscheme.

45 original IB-style questions on D2.2, written from the 2025 guide: 21 multiple-choice, 15 short-answer, 6 data-based, 2 extended-response part, 1 drawing. Below is a 20-mark higher-level practice paper built from them, ready to hand out as a class quiz or homework, or to sit yourself and mark against the scheme. Print it, project it, or build a fresh one on the same topic.

What the guide asks for

0 statements at SL and HL, 11 additional higher level.

  1. D2.2.1HL Gene expression as the mechanism by which information in genes has effects on the phenotype
  2. D2.2.2HL Regulation of transcription by proteins that bind to specific base sequences in DNA
  3. D2.2.3HL Control of the degradation of mRNA as a means of regulating translation
  4. D2.2.4HL Epigenesis as the development of patterns of differentiation in the cells of a multicellular organism
  5. D2.2.5HL Differences between the genome, transcriptome and proteome of individual cells
  6. D2.2.6HL Methylation of the promoter and histones in nucleosomes as examples of epigenetic tags
  7. D2.2.7HL Epigenetic inheritance through heritable changes to gene expression
  8. D2.2.8HL Examples of environmental effects on gene expression in cells and organisms
  9. D2.2.9HL Consequences of removal of most but not all epigenetic tags from the ovum and sperm
  10. D2.2.10HL Monozygotic twin studies
  11. D2.2.11HL External factors impacting the pattern of gene expression

In the bank for D2.2

  • 21 multiple-choice
  • 15 short-answer
  • 6 data-based
  • 2 extended-response part
  • 1 drawing
  • 45 higher level only

Every question is original and tagged to a guide statement. See the whole bank →

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The practice paper

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Biology · topic quiz
Higher level · topic practice, not an exam format
30 minutes20 marks

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Covers D2.2 Gene expression
Name:
1.

Most gene regulation in cells occurs at which stage?

[1]
  1. During DNA replication in S phase
  2. At transcription, when mRNA is made
  3. During mitosis and cytokinesis
  4. After the protein has been secreted
2.

How does methylation of histones (in nucleosomes) affect transcription?

[1]
  1. It activates or represses, depending on the residue
  2. It adds negative charge that repels polymerase
  3. It blocks restriction enzymes, aiding transcription
  4. It always prevents transcription by condensing DNA
3.

Blood cells from people living in a city with high air pollution have fewer methyl tags on the promoter of a gene involved in inflammation than blood cells from people living in a nearby rural area. Which conclusion is best supported by this observation?

[1]
  1. Air pollution has caused a mutation in the promoter, so the base sequence of the gene has changed
  2. An environmental factor has altered the expression of a gene without changing its base sequence
  3. The people living in the city must have inherited a different allele of the gene from their parents
  4. Air pollution has removed the gene from the blood cells, so it can no longer be expressed at all
4.

Which row correctly distinguishes the genome, transcriptome and proteome of a cell?

[1]
RowGenomeTranscriptomeProteome
A.all proteins madeall RNA presentall genetic material
B.all genetic materialall RNA present (transcribed)all proteins made
C.all genes expressedall DNAall amino acids
D.all genetic materialall proteinsall RNA
  1. Row A
  2. Row B
  3. Row C
  4. Row D
5.

A neuron and a liver cell from the same person contain the same genes but make different proteins. How is this possible?

[1]
  1. The two cell types contain different sets of genes after losing the ones they did not need during differentiation
  2. The genetic code is read differently in different cell types, so the same gene gives different proteins
  3. Neurons contain the full set of DNA whereas liver cells retain only the RNA copies of the genes they use
  4. Different genes are transcribed in the two cell types because different transcription factors are active
6.

What is meant by gene expression?

[1]
  1. The inheritance of a gene from parents
  2. The duplication of a gene in replication
  3. The mutation of a gene over time
  4. The use of a gene's information in the cell
7.

Cultures of the bacterium Escherichia coli were transferred from a medium lacking the amino acid tryptophan to a medium containing it. Within a few minutes the bacteria stopped producing the enzymes that synthesize tryptophan. Suggest how tryptophan brings about this change in gene expression, and the advantage to the bacterium.

[3]
8.

Explain why studies of monozygotic (identical) twins are valuable for investigating epigenetics.

[2]
9.

Outline how the degradation of mRNA contributes to the regulation of gene expression.

[3]
10.

Some biologists claim that epigenetics revives Lamarck's idea of the inheritance of acquired characteristics. Discuss this claim, linking gene expression (D2.2) to natural selection and evolution (D4.1).

[6]

Original practice questions © Biology by Bradford · CC BY-NC-SA 4.0 · Not affiliated with or endorsed by the International Baccalaureate Organization.
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Markscheme BbB-EAEAAAAAARQAO8gA

One mark per point; / separates alternative wording within a point, OR separates alternative answers, words in brackets are not required, underlined words are essential. OWTTE = or words to that effect.

1. D2.2.2 [1]
  • B: transcriptional control (transcription factors binding promoters/enhancers) is the main point of regulation; translation and protein degradation add further control;
2. D2.2.6 [1]
  • A: unlike DNA (promoter) methylation, which silences, histone methylation is context-dependent: marks at some residues open chromatin, at others compact it, part of the "histone code";
3. D2.2.8 [1]
  • B: methylation of a promoter is an epigenetic tag that represses transcription, so fewer tags mean more expression of the gene in response to the environment, with no change to the DNA sequence; A confuses an epigenetic change with a mutation; C is not supported, since methylation patterns respond to the environment and the groups were not tested for alleles; D fails because reduced methylation increases rather than abolishes expression, and genes are not removed from cells;
4. D2.2.5 [1]
  • B: genome = total DNA (fixed for the organism); transcriptome = RNA currently transcribed; proteome = proteins currently made; the latter two vary between cell types and over time;
5. D2.2.4 [1]
  • D: differential gene expression, not differences in the genome, produces different cell types;
6. D2.2.1 [1]
  • D: expression = using the gene: transcription to RNA and (for protein-coding genes) translation to polypeptide, producing the phenotype;
7. D2.2.11 [3 max]
  • tryptophan acts as an external factor / biochemical from the environment that changes the pattern of gene expression;
  • tryptophan binds to a (repressor) protein / transcription factor, changing its shape and activating it;
  • the active repressor binds to a specific base sequence in the DNA near the promoter of the genes for tryptophan synthesis;
  • (so) RNA polymerase cannot transcribe the genes / no mRNA is made, so the enzymes are no longer produced;
  • advantage: the bacterium does not waste energy and amino acids making enzymes for a substance that is already available, OWTTE;

Accept any mechanism in which tryptophan alters the binding of a protein to DNA and so blocks transcription. Do not accept tryptophan inhibiting the enzymes directly as the change in gene expression.

8. D2.2.10 [2 max]
  • monozygotic twins have (essentially) identical genomes;
  • (so) differences between them cannot be genetic, they must reflect environment/epigenetic changes;
  • comparing twins (raised apart / as they age) separates the contributions of genes and environment, e.g. diverging methylation patterns with age, OWTTE;
9. D2.2.3 [3 max]
  • mRNA molecules persist for different lengths of time before being broken down (by nucleases);
  • short-lived mRNA is translated few times, long-lived mRNA many times;
  • (so) the amount of protein made per transcription event is controlled;
  • allows rapid switching-off of expression when the mRNA supply stops, OWTTE;
10. D2.2.7 [6 max]
  • Lamarck proposed that characteristics acquired during an organism's life are passed to its offspring; the Darwinian view is that heritable variation arises independently of need and is then selected;
  • epigenetic marks (DNA methylation, histone modification) can change gene expression in response to the environment during life;
  • some marks can persist through cell division and, in some organisms, be transmitted to offspring (transgenerational epigenetic inheritance);
  • so in a limited sense an environmentally-acquired state can be inherited, resembling Lamarck's idea;
  • however, epigenetic marks are usually reset between generations and are generally reversible/short-lived, unlike changes to the DNA base sequence;
  • the base sequence (alleles) is still not directed by need — mutation remains random — so long-term evolution still proceeds by natural selection acting on genetic variation;
  • (therefore) epigenetics adds a mechanism of environmental influence but does not overturn Darwinian evolution, OWTTE;

Cross-theme synthesis D2.2 ↔ D4.1; Nature of Science; balanced Discuss required.

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