# A tumour forms when cells in the body divide in an uncontrolled way. Explain how changes in the normal cell cycle lead to the formation of a tumour.

> Edexcel A-Level Biology A: Salters-Nuffield (9BN0) — 2.2 Cell cycle and mitosis · Explain · 5 marks

> Cancer is a non-communicable disease caused by changes in the cell that lead to uncontrolled growth and division. Normally, the cell cycle is tightly regulated so that new cells are only produced when the body requires them.

## Mark scheme (5 marks)

1. The cell cycle involves cell growth and DNA replication before cell division (mitosis)
2. Changes / mutations occur in the cell that disrupt the normal regulation of the cell cycle
3. Mitosis / cell division occurs too frequently or does not stop when it should
4. This produces a mass of cells / a tumour because the daughter cells themselves continue to divide uncontrollably
5. The daughter cells produced are genetically identical to the parent cell (so the change / mutation is passed on to all new cells)

## Key terms

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

## Related

- [Revision notes for Edexcel A-Level Biology A: Salters-Nuffield (9BN0)](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-tumour-forms-when-cells-in-c64a0047) · Published by Druglandscape Ltd.