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D1.2.1—Transcription

Transcription produces an RNA copy of gene information when RNA polymerase uses one DNA strand as a complementary template for mRNA synthesis.

Syllabus
First assessment 2025
Objective
D1.2.1
Level
SL

Exam analysis

Chance of appearing4%of analysed past papers
Latest appearanceMay 2025
Most common paperPaper1
Typical marks1–4

Common command terms

  • State
  • Outline
  • Explain
  • Describe
  • Distinguish

Scoring notes

Common mistake
Confusing transcription with translation by naming ribosomes or amino acids instead of RNA polymerase and mRNA.

Recent exam appearances

May 2025Paper2 ["SL"] · TZ37(b)[ 4 ]D1.2.1—Transcription
November 2024Paper1 ["SL"] · TZ17[ 1 ]D1.2.1—Transcription
May 2019Paper2 ["SL"] · TZ17(a)[ 4 ]D1.2.1—Transcription
May 2015Paper1 ["SL"] · TZ111[ 1 ]D1.2.1—Transcription
November 2014Paper1 ["SL"] · TZ09[ 1 ]D1.2.1—Transcription
Practice this objective

Coverage 2012–2025 · Updated 16 Jul 2026

Transcription Copies a Gene into mRNA

Transcription is the synthesis of an RNA strand using one DNA strand as the template.

RNA polymerase binds the selected DNA region, separates a short section, matches RNA nucleotides to exposed template bases and joins the nucleotides into RNA.

DNA template exposed → complementary RNA nucleotides pair → RNA polymerase forms the RNA backbone → RNA separates and DNA re-forms its double helix.

For a protein-coding gene, RNA polymerase produces an mRNA transcript whose base sequence can later be translated.

Transcription synthesizes RNA, not DNA or polypeptide. Promoter/transcription-factor detail belongs to the later HL initiation objective.

Transcription exam focus

Assessment in practice

1–4 marks
How it is assessed

This objective is assessed through structured response, commonly using State / Outline / Explain.

Command terms

State / Outline / Explain / Describe / Distinguish

What earns marks

Build the answer around this relationship: Transcription copies one DNA strand into an RNA molecule.

Watch for

Confusing transcription with translation by naming ribosomes or amino acids instead of RNA polymerase and mRNA.

Representative question

Question 1

[Maximum number: 8]

Explain the process of transcription in prokaryotes.

Core Protein Synthesis

  • Transcription: RNA polymerase builds complementary mRNA from the DNA template; A pairs with U and C with G.
  • Translation: ribosomes read mRNA codons 5′ to 3′ while tRNA anticodons deliver specific amino acids for peptide-bond formation.
  • Genetic code: codons are triplets; the code is degenerate and almost universal, with start and stop signals. Use mRNA—not DNA—when reading a code table.
  • Information flow: codon order determines amino-acid sequence, which determines protein folding and function.
  • Expression and variation: cells regulate which genes are transcribed. A mutation may change a codon, primary structure and phenotype, as in sickle-cell haemoglobin.

Concept essentials

  • Transcription copies one DNA strand into an RNA molecule.
  • RNA polymerase binds DNA, separates the strands and joins RNA nucleotides.
  • The antisense strand provides the template for complementary RNA base pairing.
  • Eukaryotic transcription occurs in the nucleus and can be followed by RNA processing.