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D1.1.1—DNA replication

DNA replication explains how DNA is copied, checked, amplified or analysed through specific strand relationships, enzyme functions and molecular techniques.

Syllabus
First assessment 2025
Objective
D1.1.1
Level
SL

Exam analysis

Chance of appearing2%of analysed past papers
Latest appearanceNovember 2015
Most common paperPaper1
Typical marks1–3

Common command terms

  • Identify
  • Explain

Scoring notes

Common mistake
Saying both parental strands stay together instead of one parental strand entering each daughter molecule.

Recent exam appearances

November 2015Paper1 ["SL"] · TZ09[ 1 ]D1.1.1—DNA replication
November 2013Paper2 ["SL"] · TZ03(b)[ 3 ]D1.1.1—DNA replication
May 2012Paper1 ["SL"] · TZ19[ 1 ]D1.1.1—DNA replication
Practice this objective

Coverage 2012–2015 · Updated 16 Jul 2026

DNA Replication Copies the Genome Before Division

DNA replication produces exact copies of DNA with identical base sequences, apart from rare copying errors.

Accurate copies preserve genetic information when cells or organisms reproduce. In multicellular organisms, replication supplies genomes for cell division during growth and replacement of damaged or worn tissues.

Original DNA sequence → replication → two matching DNA molecules → genetic continuity in reproduction, growth and tissue replacement.

Before a skin cell divides to replace lost tissue, its DNA is copied so both daughter cells can inherit the same base sequence.

Replication copies DNA; transcription makes RNA and translation makes polypeptide. ‘Identical’ describes base-sequence information, not two newly synthesized strands without templates.

DNA replication

Assessment in practice

1–8 marks
How it is assessed

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

Command terms

Identify / Explain

What earns marks

Build the answer around this relationship: DNA replication depends on matching each strand, enzyme or laboratory step to its exact function.

Watch for

Saying both parental strands stay together instead of one parental strand entering each daughter molecule.

Representative question

Question 1

[Maximum number: 8]

Growth in living organisms includes replication of DNA. Explain DNA replication.

Core DNA Replication

DNA replication produces exact DNA copies before cell division and maintains genetic continuity for reproduction, growth, and tissue replacement. Semi-conservative replication gives each new DNA molecule one original strand and one new strand; complementary base pairing and Meselson-Stahl isotope evidence support the model. Helicase unwinds DNA and breaks hydrogen bonds; DNA polymerase joins complementary nucleotides to build new strands. PCR amplifies selected DNA using primers, temperature cycles, and Taq polymerase; gel electrophoresis separates DNA fragments by size and charge. PCR and gel electrophoresis support DNA profiling for forensic identification and paternity testing.

Concept essentials

  • DNA replication depends on matching each strand, enzyme or laboratory step to its exact function.
  • Template strands and complementary base pairing give dna replication its copying accuracy.
  • DNA replication is clearer when amplification, separation and profiling are not confused.
  • Molecular evidence for dna replication must be interpreted from bands, isotopes, primers or enzyme roles.