The G1 and G2 phases are referred to as 'gap' phases - their jobs are to monitor the cell between its major phases and ensure that it is fit to move into the next respective phase; either the S phase (DNA replication) or the M phase (mitosis), respectively. They are often known as 'checkpoints' as it is during these periods that both the cell's internal and external environments are checked and monitored. This monitoring involves ensuring the cell is suitable to progress through the cell cycleor whether it needs a little more time to prepare.
The G2 phase occurs between the S phase and the M phase. It is a crucial stage as it ensures the S phase has been carried out correctly and prepares the cell for mitosis. This preparation involves making sure the DNA is intact and checking chromosome duplication has occurred, without which the M phase cannot proceed. Any found errors (such as damaged DNA) can then be corrected and repaired by the cell during the G2 phase.
- ↑ Delete Alberts, Bray, Hopkin, Johnson, Lewis, Raff, Roberts, Walter (2014) Essential Cell Biology, 4th edn., New York: Garland Science, Taylor &amp;amp;amp;amp;amp;amp; Francis Group.