IGCSE Biology glossary
Mutation
Biology editorial review is supported by the named review panel. Reviewer participation may vary by guide. Checked against Cambridge IGCSE Biology 0610 (2026–2028); last reviewed August 2026.
Definition
A random genetic change, which may produce a new allele or change a gene or chromosome.
What to include in an exam answer
the key term is 'random' (mutations are spontaneous and not directed toward a need). Examiners reward linking mutation to the origin of new alleles, which is the source of genetic variation acted on by natural selection. Mention that ionising radiation and some chemicals increase the rate of mutation. A common error is saying mutations are 'always harmful'; many are neutral and some are advantageous.
Example in context
On the source of new variation: 'A new allele for antibiotic resistance arose by random mutation, and bacteria with this allele survived and reproduced.'
Related syllabus topic
Variation & selection