# Explain how complementary base pairing contributes to the stability of a DNA molecule and to the accurate copying of genetic information.

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

## Mark scheme (4 marks)

1. Complementary base pairing describes how A pairs with T and C pairs with G (weak hydrogen bonds form between the complementary base pairs)
2. The hydrogen bonds between complementary base pairs hold the two strands of the double helix together, giving the molecule stability
3. When DNA is replicated, the two strands separate and each strand acts as a template
4. Because each base can only pair with its complementary base, the sequence of bases is copied accurately, producing two identical DNA molecules

## Key terms

- [complementary base pairing](https://www.gradenine.co.uk/glossary/complementary-base-pairing)
- [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 "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/explain-how-complementary-base-pairing-contributes-644d7639) · Published by Druglandscape Ltd.