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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
HL

Exam analysis

Chance of appearing1%of analysed past papers
Latest appearanceNovember 2016
Most common paperPaper2
Typical marks8

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 2016Paper2 ["HL"] · TZ07(c)[ 8 ]D1.1.1—DNA replication

Coverage 2016–2016 · Updated 16 Jul 2026

DNA Must Be Copied Before a Cell Divides

DNA replication produces a second DNA molecule with the same base sequence as the original, apart from rare errors.

chromosome DNA → replication during interphase → two DNA copies → cell division → one complete genome enters each daughter cell

A cell copies its DNA before dividing so each daughter cell receives a DNA copy.
Biological context Why replication is required
reproduction genetic information passes to new cells or offspring
growth cell number increases without losing the genome
tissue replacement new cells inherit the instructions needed for their function

Reconstruct the Core Replication Argument

need two genomes → helicase separates the original strands → each old strand acts as a template → complementary nucleotides pair → DNA polymerase links the new backbone → two matching double helices form

Feature to check Correct outcome
sequence complementary copying preserves the base-pair sequence
strand origin each product has one old strand and one new strand
biological result a complete genome can pass to each daughter cell

A model explains how copying could occur; the Meselson–Stahl band pattern provides experimental evidence that the one-old-one-new strand distribution actually occurs.

DNA replication

[ 8 ]

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

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.