# Describe the structure of a DNA molecule.

> Edexcel GCSE Biology (1BI0) — 3.3 DNA structure · Describe · 4 marks

## Mark scheme (4 marks)

1. DNA is a double-stranded polymer / made of two strands
2. The two strands are wound / twisted to form a double helix
3. DNA is made of monomers called nucleotides, each consisting of a sugar, a phosphate group and one of four bases (A, T, C or G)
4. Complementary base pairing holds the two strands together, with A pairing with T and C pairing with G, via hydrogen bonds

## Key terms

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

## Related

- [Revision notes for Edexcel GCSE Biology (1BI0)](https://www.gradenine.co.uk/learn)
- [How to answer "Describe" questions](https://www.gradenine.co.uk/tools/command-word-cheatsheet)
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Source: [GradeNine](https://www.gradenine.co.uk/q/describe-the-structure-of-a-dna-a16902ee) · Published by Druglandscape Ltd.