Cell cycle

Cell cycle is a series of events that leads to the division and duplication of cells.

In prokaryotic cells the cycle is called binary fission. This type of division starts with the replication of one DNA molecule. Then, the DNA is pulled to the poles of the cell and increases its size before splitting. The growth of a new cell wall begins to separate the cell and when fully developed leads to the split of the cell.

In cells with a nucleus (eukaryotic) the cycle includes 4 phases: G₁, S, G₂ and M. There is also a resting phase where the cell has left the cycle and stopped dividing (G₀). In G₁ the cell increase in size and function normally. At some point (the first checkpoint), the cell becomes “committed” to the cycle no longer requiring extracellular stimuli (this is called restriction point). Next comes the DNA replication (synthesis or S phase).  During G₂­ phase the cell continue to grow. When the second checkpoint is reached and if all the requirements are met then the cell is ready to enter the last phase – mitosis (M). Here the cell stops growing and directs its energy to the division into the daughter cells. The last checkpoint is the metaphase, which ensures that the cell is ready to complete the cycle.

 

                                                                                                    Nguyen Quynh Anh, Renata Oliveira

                                                                                                                                    Applied Biology