Explain how a mutation could lead to a change in the characteristics of an organism.

Eduqas GCSE Biology — 2.4.2 Evolution and natural selection · Explain · 4 marks · View as Markdown

Written & reviewed by James Millett — Biology (Imperial College London), PGCE Science (University of Cambridge).

Mutations are random changes in DNA. They can have a neutral, beneficial or damaging effect on the phenotype.

Model answer (4 marks)

A mutation is a random change in the DNA base sequence.
A change in the DNA base sequence alters the sequence of amino acids coded for.
This produces a different or altered protein.
The different protein changes the phenotype or observable characteristic of the organism.

Examiner tips

Use the exact sequence of points from the mark scheme; each sentence earns a mark.
Show the logical flow from DNA change to phenotype change.
Keep sentences short and to the point.
Use UK spelling (phenotype).

Common mistakes

Confusing mutation with natural selection; they are different concepts.
Using vague terms like ‘change’ without specifying DNA, protein, or phenotype.
Omitting the step that the altered DNA changes the amino‑acid sequence.

Mark scheme (4 marks)

A mutation is a random change in the DNA / base sequence
A change in the DNA base sequence alters the sequence of amino acids coded for
This produces a different / altered protein
The different protein changes the phenotype / observable characteristic of the organism

Key terms in this question

mutation