In the cell cycle, this checkpoint checks internal and external conditions. These conditions are:
* Size, is it big enough to divide?
* Nutrients, is there enough energy to divide?
* Molecular signals, any positive cues from neighbors
* DNA integrity, is any DNA damaged?
If all checks out the cells will enter the S phase and will be irreversibly committed to division. If not continued it will stay in a resting state called G0
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