# Describe the structure of a DNA molecule and explain how this structure allows DNA to be copied accurately during cell division.

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

## Mark scheme (5 marks)

1. DNA is made up of two strands
2. The strands are twisted into a double helix
3. The strands are held together by bases / base pairs (adenine pairs with thymine; cytosine pairs with guanine)
4. During copying, the two strands separate / unzip
5. Each strand acts as a template so that complementary/free bases pair up to produce two identical copies

## 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 "Describe and 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/describe-the-structure-of-a-dna-c4fcee01) · Published by Druglandscape Ltd.