# Explain why not all mutations lead to a change in an organism's phenotype.

> Edexcel GCSE Biology (1BI0) — 3.5 Variation and mutation · Explain · 4 marks

> Mutations are random changes in the base sequence of DNA. Scientists studying a population of wild mice found that, despite many mutations being present across individuals, very few of these mutations produced any observable difference in the mice.

## Mark scheme (4 marks)

1. A mutation may be neutral / have no effect on the organism
2. A mutation in a non-coding region of DNA does not code for a protein / does not affect protein production
3. Even if a gene is mutated, the same amino acid may still be produced / the mutation may be silent
4. If the protein / enzyme produced is unchanged, the phenotype will not change

## Key terms

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

## Related

- [Revision notes for Edexcel GCSE Biology (1BI0)](https://www.gradenine.co.uk/learn)
- [How to answer "Explain" questions](https://www.gradenine.co.uk/tools/command-word-cheatsheet)
- [Practice this with AI marking (free)](https://www.gradenine.co.uk/start)

---
Source: [GradeNine](https://www.gradenine.co.uk/q/explain-why-not-all-mutations-lead-d36a62cf) · Published by Druglandscape Ltd.