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D1.2.17 (HL)—Translation initiation

Translation initiation and ribosomal tRNA sites organize start-codon recognition, amino acid entry, peptide transfer and tRNA exit during protein synthesis.

Syllabus
First assessment 2025
Objective
D1.2.17
Level
HL

Exam analysis

Chance of appearing5%of analysed past papers
Latest appearanceMay 2025
Most common paperPaper1
Typical marks1–3

Common command terms

  • Outline

Scoring notes

Common mistake
Putting the initiator tRNA into the E site or A site instead of linking initiation to the start codon and P site.

Recent exam appearances

May 2025Paper1A ["HL"] · TZ311[ 1 ]D1.2.17 (HL)—Translation initiation
November 2023Paper2 ["HL"] · TZ22(c)[ 3 ]D1.2.17 (HL)—Translation initiation
November 2022Paper1 ["HL"] · TZ028[ 1 ]D1.2.17 (HL)—Translation initiation
November 2019Paper1 ["HL"] · TZ027[ 1 ]D1.2.17 (HL)—Translation initiation
May 2017Paper2 ["HL"] · TZ26(b)[ 4 ]D1.2.17 (HL)—Translation initiation
Practice this objective

Coverage 2017–2025 · Updated 16 Jul 2026

Concept essentials

  • The small ribosomal subunit binds mRNA early in initiation.
  • The start codon AUG establishes the reading frame for translation.
  • The A site receives incoming aminoacyl-tRNA.
  • The P site holds the growing polypeptide, and the E site releases empty tRNA.
ConceptIB Biology HL