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B2.3.1—Differentiation after fertilization

Differentiation produces specialized cells when the same genome is used differently through selective gene expression and developmental signalling gradients after fertilization.

Syllabus
First assessment 2025
Objective
B2.3.1
Level
SL

Exam analysis

Chance of appearing3%of analysed past papers
Latest appearanceMay 2025
Most common paperPaper1
Typical marks1

Common command terms

  • Identify
  • Explain

Scoring notes

Common mistake
Saying differentiated cells contain different chromosomes or lose unused genes.

Recent exam appearances

May 2025Paper1A ["SL"] · TZ210[ 1 ]B2.3.1—Differentiation after fertilization
May 2022Paper1 ["SL"] · TZ26[ 1 ]B2.3.1—Differentiation after fertilization
May 2013Paper1 ["SL"] · TZ23[ 1 ]B2.3.1—Differentiation after fertilization
May 2010Paper1 ["SL"] · TZ23[ 1 ]B2.3.1—Differentiation after fertilization
Practice this objective

Coverage 2010–2025 · Updated 15 Jul 2026

Concept essentials

  • Differentiated cells usually retain the same genome as other body cells.
  • Different cell types express different sets of genes.
  • Protein differences provide biochemical evidence that differentiation has begun.
  • Signalling gradients can direct unspecialized cells toward specific fates.
ConceptIB Biology SL