However, if there has been an incorrectly copied chromosome, the cell will remain in S-phase till the mistake is corrected, or it will go through apoptosis, right? So, there is no guarantee that it will divide if there's been a mistake.
DNA stands for deoxyribonucleic acid and is a self-replicating material that nearly all living organisms have. DNA carries the organism's genetic information. Cells, which contain DNA, normally divide to multiply, causing the organism to grow, reproduce, and replenish dead cells.
At the G1 checkpoint, the cell ensures that there is no damage to DNA or threat from external factors. If damage or threat is detected, the cells will not be allowed to complete the process and divide. If the signal is given that everything is okay, then the cells will complete the process and divide.