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D2.2.8 (HL)—Environmental effects on expression

Environmental factors can alter gene expression through signalling, transcript changes and epigenetic modifications such as DNA methylation in cells and organisms.

Syllabus
First assessment 2025
Objective
D2.2.8
Level
HL

Exam analysis

Chance of appearing3%of analysed past papers
Latest appearanceMay 2018
Most common paperPaper2
Typical marks1–3

Common command terms

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Scoring notes

Common mistake
Treating altered expression as a necessary DNA base-sequence mutation.

Recent exam appearances

May 2018Paper1 ["HL"] · TZ211[ 1 ]D2.2.8 (HL)—Environmental effects on expression
May 2018Paper2 ["HL"] · TZ21(e)[ 3 ]D2.2.8 (HL)—Environmental effects on expression
May 2017Paper2 ["HL"] · TZ11(f)(ii)[ 2 ]D2.2.8 (HL)—Environmental effects on expression
Practice this objective

Coverage 2017–2018 · Updated 16 Jul 2026

Concept essentials

  • Environmental conditions can alter gene expression.
  • Changes in mRNA abundance show altered transcription or transcript level.
  • DNA methylation patterns can be changed by environmental factors.
  • Different light regimes can produce different transcript patterns in plants.
ConceptIB Biology HL