The cell cycle consists of four key stages that cells undergo in order to grow and divide. The cycle starts when a cell is first produced, the final stage is when the cell divides and the two daughter cells then start the same process again. The four stages are as follows:
The cycle can be classed as two main categories: interphase and the mitotic phase.
Interphase
Interphase in the process in which cells prepare to divide and takes place as the cell carries out its normal functions. During interphase the ATP content of the cell is increased in order to provide enough energy for cell division.
G1 is called Gap Phase 1 and is the first step in the cell cycle that takes place after cell division. In this phase the cell grows and produces new organelles and proteins.
The next stage is called Synthesis (S) and during this stage the DNA of the cell is replicated (by semi-conservative replication). A copy of the cells centrosome (an organelle consisting of centrioles and complex proteins) is also produced.
The final stage of interphase is G2 which stands for Gap Phase 2. During this phase the cell continues to grow, more organelles are made and any proteins required for cell division are produced.
The Mitotic Phase
Once interphase is complete the cell divides by mitosis. For more on mitosis click here.
Once mitosis is complete some cells immediately begin the cell cycle again, starting with G1. This is particularly true for cells that divide rapidly, such as the cells of an embryo.
Other cells however enter a phase called G0.
G0
Some cells don’t divide, or divide slowly. These cells can leave the G1 stage of interphase and enter a phase called G0. This is a phase in which cells aren’t preparing for division and just carry out their normal functions. Cells can leave the G0 phase and continue with interphase if they receive the correct signals or they can remain in G0 permanently.
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