# A tumour is a mass of cells that forms when the cell cycle is no longer controlled. Explain how a fault in the cell cycle leads to the formation of a tumour, and describe what this means for the affected cells.

> Pearson Edexcel A-Level Biology A (9BI0) — 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, cells complete the cell cycle in a highly regulated way, producing two genetically identical daughter cells.

## Mark scheme (5 marks)

1. The cell cycle normally controls when cells grow and divide, but a change/fault in the cell causes this control to be lost
2. Cells undergo uncontrolled growth and division / divide repeatedly without stopping
3. Mitosis produces large numbers of new daughter cells / cells accumulate in large numbers
4. These cells form a mass / tumour as they continue to accumulate
5. The daughter cells produced are genetically identical to the original changed/faulty cell, so the fault is passed on to all new cells

## Key terms

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

## Related

- [Revision notes for Pearson Edexcel A-Level Biology A (9BI0)](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-is-a-mass-of-a6264fc4) · Published by Druglandscape Ltd.