# A student says: 'Every cell in a human body contains the same DNA, so every cell must make the same proteins.' Explain why this statement is incorrect.

> AQA A-Level Biology (7402) — 3.4.2 DNA and Protein Synthesis · Explain · 5 marks

> Human body cells are specialised for different functions. For example, a pancreatic cell produces the hormone insulin, whereas a muscle cell does not.

## Mark scheme (5 marks)

1. DNA contains genes / sections of DNA that code for proteins
2. All body cells contain the same genes / the same DNA sequence
3. Only certain genes are switched on / expressed in a particular cell type
4. Only the mRNA produced from active/expressed genes is used to make protein (in that cell)
5. Therefore different cell types produce different proteins / reference to example (e.g. pancreatic cells produce insulin but muscle cells do not)

## Key terms

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

## 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-says-every-cell-in-2763b48f) · Published by Druglandscape Ltd.