CourseCourseQuestionQuestionDocumentDocument

D1.2.6—Roles in translation

mRNA, tRNA and ribosomes have distinct roles that coordinate codon reading, amino acid delivery and peptide bond formation during translation.

Syllabus
First assessment 2025
Objective
D1.2.6
Level
HL

Exam analysis

Chance of appearing4%of analysed past papers
Latest appearanceMay 2022
Most common paperPaper1
Typical marks1–2

Common command terms

  • Identify
  • Outline
  • Explain

Scoring notes

Common mistake
Swapping the roles of codons and anticodons between mRNA and tRNA.

Recent exam appearances

May 2022Paper2 ["HL"] · TZ14(c)[ 2 ]D1.2.6—Roles in translation
May 2021Paper1 ["HL"] · TZ127[ 1 ]D1.2.6—Roles in translation
November 2020Paper1 ["HL"] · TZ028[ 1 ]D1.2.6—Roles in translation
May 2017Paper2 ["HL"] · TZ12(b)[ 2 ]D1.2.6—Roles in translation
November 2016Paper1 ["HL"] · TZ026[ 1 ]D1.2.6—Roles in translation

Coverage 2016–2022 · Updated 16 Jul 2026

mRNA, tRNA and the Ribosome Divide Translation Work

Component Information or material carried Translation job
mRNA ordered codons supplies the sequence to be read
tRNA one anticodon and its attached amino acid matches a codon and delivers the corresponding amino acid
small ribosomal subunit mRNA-binding site positions the message for decoding
large ribosomal subunit A, P and E sites positions tRNAs and catalyses peptide-bond formation

Translation is accurate only when all three information links agree: the mRNA codon, the tRNA anticodon and the amino acid attached to that tRNA.

The ribosome does not choose amino acids by recognizing their chemical identity. It accepts charged tRNAs whose anticodons pair with the exposed codons.

Trace Information—and the Places Where It Can Change

DNA template → complementary mRNA → codons read 5′→3′ → charged tRNAs selected → peptide bonds join amino acids → polypeptide primary structure

Checkpoint Question to ask
transcription Is the mRNA complementary to the template and written 5′→3′?
code table Are mRNA codons grouped from the correct start?
tRNA selection Does the anticodon pair and is the tRNA correctly charged?
elongation Has the ribosome advanced one codon while the chain remains on the peptidyl-tRNA?
mutation Did the codon, amino acid or reading frame actually change?

A sequence change matters biologically only through a causal path: altered primary structure → altered interactions or folding → altered protein activity → possible cellular or organism effect.

Roles in translation

[ 7 ]

Explain the role of RNA in translation, resulting in the formation of polypeptide chains.

Concept essentials

  • mRNA supplies codons that are read by the ribosome.
  • tRNA carries a specific amino acid and has a complementary anticodon.
  • tRNA-activating enzymes attach amino acids to the correct tRNA molecules.
  • Ribosomes hold mRNA and tRNA together so peptide bonds can form.