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D2.2.11 (HL)—External factors

External factors regulate gene expression through hormone signalling, transcription factors and bacterial operon responses to substrates or products in cells.

Syllabus
First assessment 2025
Objective
D2.2.11
Level
HL

Concept essentials

  • Hormones can regulate transcription through receptors and transcription factors.
  • The lac operon is induced when lactose prevents repressor binding.
  • The trp operon is repressed when tryptophan is abundant.
  • External factors alter gene activity without necessarily changing DNA sequence.
ConceptIB Biology HL