# A student states: 'Every cell in a human body contains the same DNA, yet cells look and behave very differently from one another.' Explain how cells with identical DNA can produce different proteins, and why the order of bases in DNA is important for protein production.

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

## Mark scheme (5 marks)

1. Different genes are expressed (switched on) in different cell types
2. A gene is a section of DNA that codes for a specific protein
3. The order/sequence of bases in a gene determines the order of amino acids in a protein
4. Each amino acid is coded for by a sequence of three bases (a triplet / codon)
5. The order of amino acids determines the shape/structure of the protein, so different proteins have different functions

## Key terms

- [DNA](https://www.gradenine.co.uk/glossary/dna)

## 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/a-student-states-every-cell-in-00767f83) · Published by Druglandscape Ltd.