# Explain the significance of the G1 and G2 checkpoints in the cell cycle, distinguishing between the conditions each checkpoint monitors.

> IB DP Biology Higher Level (2023 syllabus) — D2.1 Cell and nuclear division · Explain · 4 marks

## Mark scheme (4 marks)

1. G1 checkpoint assesses whether the cell has sufficient nutrients/size/growth factors to proceed with DNA replication
2. G2 checkpoint monitors whether DNA replication has been completed accurately and checks for DNA damage before mitosis begins
3. If conditions are not met at either checkpoint, cyclin-dependent kinase (CDK) activity is inhibited / cyclin levels do not rise, halting progression through the cycle
4. The checkpoints are significant because they prevent propagation of damaged or incompletely replicated DNA, reducing the risk of mutations that could lead to cancer / uncontrolled cell division

## Key terms

- [G2 checkpoint](https://www.gradenine.co.uk/glossary/g2-checkpoint)

## Related

- [Revision notes for IB DP Biology Higher Level (2023 syllabus)](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-the-significance-of-the-g1-79d306e8) · Published by Druglandscape Ltd.