The cell cycle can simply be split into interphase and mitosis, however you can further divide interphase into G1, G0 S-phase and G2. S-phase is the primary period in which DNA of the cell is replicated. Via semi-conservative replication, the cell effectively doubles its amount of DNA and retains its original ploidy. As DNA replication must be correct, and damage or mistakes in the process must be avoided to prevent cell death or disease, the proof-reading action of DNA polymerase is vital during S-phase.
Another feature of S-phase is the regulation of cell progress by the activity of cyclins and cyclin-dependent kinases at checkpoints before and after S-phase. Such checkpoints ensure that the cell has undergone all growth and changes needed to progress to the next stage of its life, and without proper regulation a cell can enter necrosis or proliferation to cause tumours .
- ↑ http://www.nature.com/scitable/topicpage/dna-replication-and-checkpoint-control-in-s-14202419
- ↑ http://cyberbridge.mcb.harvard.edu/mitosis_4.html