# Explain why a change in the base sequence of a gene may not always result in a change in the amino acid sequence of the protein produced.

> AQA A-Level Biology (7402) — 3.1.5 Nucleic Acids · Explain · 5 marks

## Mark scheme (5 marks)

1. The base sequence of a gene codes for the amino acid sequence of a protein
2. Bases are read / coded in groups of three (triplets / codons)
3. There are more possible triplet combinations than there are amino acids, so the code is degenerate / redundant
4. If the change in base sequence produces a triplet that still codes for the same amino acid, the amino acid sequence is unchanged
5. Therefore the protein produced has the same amino acid sequence / structure / function

## Key terms

- [base sequence](https://www.gradenine.co.uk/glossary/base-sequence)
- [gene](https://www.gradenine.co.uk/glossary/gene)
- [amino acid sequence](https://www.gradenine.co.uk/glossary/amino-acid-sequence)

## Related

- [Revision notes for AQA A-Level Biology (7402)](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)

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Source: [GradeNine](https://www.gradenine.co.uk/q/explain-why-a-change-in-the-03c50215) · Published by Druglandscape Ltd.