# A student says: 'DNA is just a long chain of nucleotides joined together.' Explain why this description is incomplete.

> WJEC GCSE Biology (Wales) — 2.3.1 DNA structure · Explain · 4 marks

## Mark scheme (4 marks)

1. DNA consists of TWO strands / chains (not one)
2. The two strands are twisted into a double helix
3. The strands are held together / joined by complementary base pairs
4. Specific base pairing: A pairs with T and C pairs with G

## Key terms

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

## Related

- [Revision notes for WJEC GCSE Biology (Wales)](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-dna-is-just-5cac8db0) · Published by Druglandscape Ltd.