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D1.2.13 (HL)—Initiation of transcription at promoter

Promoters are upstream non-coding DNA regions that position RNA polymerase and help initiate regulated transcription of a gene in cells.

Syllabus
First assessment 2025
Objective
D1.2.13
Level
HL

Exam analysis

Chance of appearing1%of analysed past papers
Latest appearanceMay 2024
Most common paperPaper2
Typical marks2

Common command terms

  • Explain

Recent exam appearances

May 2024Paper2 ["HL"] · TZ14(c)[ 2 ]D1.2.13 (HL)—Initiation of transcription at promoter
Practice this objective

Coverage 2024–2024 · Updated 16 Jul 2026

Promoters Position Transcription Initiation

HL only

A promoter is a DNA region where transcription machinery binds to position RNA polymerase and define where transcription begins.

Promoter sequence and associated factors determine strand choice, start site and transcription level. Opening and early RNA synthesis proceed from that positioned complex.

Name: promoter; binding factor; start site; direction of RNA synthesis.

A promoter mutation can reduce mRNA production without changing the protein-coding sequence. RNA polymerase begins at the promoter and then moves along the template, so promoter position fixes which downstream sequence is copied.

A promoter is regulatory DNA, not the entire gene or translated region.

Initiation of transcription at promoter

HL only

Assessment in practice

2 marks
How it is assessed

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

Command terms

Explain

What earns marks

Build the answer around this relationship: Promoters are non-coding DNA sequences linked to transcription start sites.

Representative question

Question 1

[Maximum number: 2]

Explain the function of a promoter in DNA.

HL Protein Synthesis Details

HL only

RNA polymerase reads template DNA 3' to 5' and synthesizes RNA 5' to 3'; ribosomes translate mRNA codons in the 5' to 3' direction. Promoters mark transcription start regions and orientation; transcription factors help RNA polymerase bind and initiate in eukaryotes. Non-coding DNA does not code for polypeptide amino acid sequences and includes introns, regulatory sequences, telomeres, rRNA genes, and tRNA genes. Eukaryotic pre-mRNA is modified before export and translation by adding a 5' cap and poly-A tail and removing introns by splicing. Alternative splicing joins different exon combinations from one pre-mRNA, so one gene can produce multiple protein variants in different cells or stages. Translation initiation assembles ribosomal subunits at the start codon AUG; initiator tRNA enters the P site and A, P, and E sites organize tRNA movement. Newly made polypeptides may be folded, cleaved, or chemically modified; preproinsulin processing to active insulin is a key example. Proteasomes degrade tagged, damaged, or unneeded proteins; amino acid recycling supports new protein synthesis and proteome quality control.

Concept essentials

  • Promoters are non-coding DNA sequences linked to transcription start sites.
  • RNA polymerase or transcription factors bind at promoter regions.
  • Promoters help determine where transcription begins.
  • Promoter activity contributes to regulation of gene expression.