# Describe how a mutation in a gene could affect the phenotype of an organism.

> WJEC GCSE Biology (Wales) — 2.4.1 Variation · Describe · 4 marks

## Mark scheme (4 marks)

1. A mutation is a random change in DNA (base sequence / nucleotide sequence)
2. A change in the DNA base sequence alters the sequence of amino acids coded for (via the triplet code)
3. This changes the structure / shape of the protein produced
4. This may change the physical characteristics (phenotype) of the organism — which may be neutral, beneficial or damaging

## Key terms

- [mutation](https://www.gradenine.co.uk/glossary/mutation)
- [phenotype](https://www.gradenine.co.uk/glossary/phenotype)

## Related

- [Revision notes for WJEC GCSE Biology (Wales)](https://www.gradenine.co.uk/learn)
- [How to answer "Describe" questions](https://www.gradenine.co.uk/tools/command-word-cheatsheet)
- [Practice this with AI marking (free)](https://www.gradenine.co.uk/start)

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Source: [GradeNine](https://www.gradenine.co.uk/q/describe-how-a-mutation-in-a-0ea3375b) · Published by Druglandscape Ltd.