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D1.3.7—Mutation as source of variation

Mutation creates new alleles and heritable variation, supplying raw genetic material on which natural selection can act in changing populations.

Syllabus
First assessment 2025
Objective
D1.3.7
Level
HL

Exam analysis

Chance of appearing1%of analysed past papers
Latest appearanceMay 2012
Most common paperPaper1
Typical marks1

Recent exam appearances

May 2012Paper1 ["HL"] · TZ134[ 1 ]D1.3.7—Mutation as source of variation
Practice this objective

Coverage 2012–2012 · Updated 16 Jul 2026

Mutation Supplies Variation for Natural Selection

Gene mutation is the original source of new alleles and therefore of all genetic variation.

Most mutations are neutral or harmful to an individual, but a population needs heritable variants for natural selection to act on. Selection changes allele frequencies; it does not create the initial DNA differences.

Mutation creates a new allele → inheritance can place it in a population → environmental conditions affect reproductive success → natural selection can change its frequency over generations.

A new allele that improves drought survival may spread when carriers leave more offspring in dry conditions, while the same allele may provide no advantage in another environment.

Mutation alone is not adaptation. The variant must be heritable and influence reproductive success in the relevant environment.

Mutation as source of variation

Assessment in practice

1 marks
How it is assessed

This objective is assessed through multiple choice.

What earns marks

Build the answer around this relationship: Mutation produces new alleles.

Representative question

Question 1

[Maximum number: 1]

What causes variation in both sexually and asexually reproducing organisms?

A

Mutations

B

Polygenic inheritance

C

Crossing over

D

Independent assortment

Core Mutation Effects

Gene mutations are changes in the base sequence of DNA; main types are substitution, insertion, deletion, and duplication. Base substitutions can create SNPs and change codons; degeneracy can make substitutions silent, missense, or nonsense. Insertions or deletions not in multiples of three cause frameshifts that alter downstream codons and often disrupt protein function. Mutations can arise from replication errors, repair errors, or chromosome damage; mutagens include chemicals, ionizing radiation, and ultraviolet radiation. Mutations occur randomly with respect to organism need or advantage; mutation rate varies with DNA sequence, gene expression, repair, and mutagen exposure. Germ-line mutations can be inherited by offspring; somatic mutations affect only descendant body cells and can contribute to cancer. Mutation is the original source of new alleles and genetic variation; many are neutral or harmful, but variation supplies material for natural selection.

Concept essentials

  • Mutation produces new alleles.
  • Heritable variation requires a change in genetic material.
  • Mutation can generate variation in both sexual and asexual organisms.
  • Natural selection acts on variation that mutation can supply.