Cell Cycle

Cells are able to replicate themselves identically so that they can proliferate and increase in number and decrease in size. They do this cyclically, with different stages preceding the division and then the final separation. This is known as the cell cycle. The cycle is composed of the G1, S, G2, and M-phase. These stages are when the cell is going to divide, there is another phase, where the cell is not going to divide. G0 is also known as the cell being in quiescence. The G1 phase stands for gap or growth phase. This is the start where the cell checks for nutrients, energy and DNA damage to make sure it is ready to replicate the genome and then split the cell. It preps for replication by making nucleotides and proteins required for DNA replication. The S phase is the synthesis phase where DNA replication occurs. G2 phase is another gap phase where the cell grows some more, checks that the cell completed DNA replication, and checks the DNA for damage. The M-Phase is where there is chromosome segregation and spindle assembly. This is the phase that houses the steps of mitosis and includes cytokinesis. Cytokinesis occurs at the end of M-phase, after the stages of mitosis are complete, and cleaves the two halves the cell so that they are separated and now two different cells.