Interphase

Interphase


=== Before a cell can enter cell division, it needs to prepare itself by replicating its genetic information and all of the organelles. All of the preparations are done during the interphase. Interphase proceeds in three stages, G1, S, and G2. Cell division operates in a cycle. Therefore, interphase is preceded by the previous cycle of mitosis and cytokenesis. ===

G1 Phase
After mitosis is complete the new daughter cell begins to accelerate its biochemical processes which were slowed down by mitosis. The length of the G1 phase is the difference from fast dividing cells to slow dividing cells. The G1 phase can be slowed by reducing the nutrients available in a system - thus the cell will take longer to build up the resources necessary for cell division. If there is a severe depletion in nutrients the cells can virtually stop growing. It is interesting to note that cells that aren't growing are always stopped in the G1 phase, being mitotically arrested. This suggests that once the cell enters the S phase, it is committed to cell division, regardless of the external cell conditions.

S Phase
The S phase begins with the replication of the cellular DNA. This is described in further detail in DNA replication (link). When the cellular DNA has been duplicated, leaving the cell with twice as many chromosomes (each chromosome is made up of two identical chromatids), the cell moves onto the G2 phase.

G2 Phase
During this phase proteins, such as kinase (which catalyzes protein phosphorylation), which are necessary for cell division are synthesized at this time. The chromosome begins to condense and the proteins necessary for construction of the mitotic spindle also are synthesized. When the chromosomes become visible the cell enters the first stage of mitosis, prophase.