# Explain how a mutation in a cell's DNA can lead to the development of cancer.

> OCR A-Level Biology B — Advancing Biology (H422) — 3.2 Disease, mutation and cancer · Explain · 5 marks

> Cancer is one of the most common diseases in the UK. It occurs when normal body cells begin to divide in an uncontrolled way, forming a tumour. Scientists know that certain factors can increase the likelihood of cancer developing.

## Mark scheme (5 marks)

1. A mutation is a change in the DNA (base sequence / genetic code) of a cell
2. Mutations can occur spontaneously or be caused by mutagens (e.g. radiation, carcinogens such as chemicals in cigarette smoke)
3. The mutation affects genes that control cell division / growth
4. The mutated cell divides uncontrollably / does not respond to normal growth signals
5. This uncontrolled division produces a mass of abnormal cells called a tumour

## Key terms

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

## Related

- [Revision notes for OCR A-Level Biology B — Advancing Biology (H422)](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-a-mutation-in-a-3d373a0e) · Published by Druglandscape Ltd.