4.7 Regulation of Cell Cycle

Cell Cycle Checkpoints

Mistakes in duplication can lead to mutations that can lead to cells being abnormal. Because of this, cell cycle checkpoints are done. 

At checkpoints, the progression of the cell cycle is halted until all parts are checked and conditions are correct to continue with duplication. Checkpoints are at the end of G1, at the G2 and M transition, and during metaphase.

Image courtesy of BioNinja.

At G1, there is a cell growth checkpoint. This check occurs at the end of the G1 growth phase. During this checkpoint, it checks whether the cell is big enough and has the proper proteins and nutrients for the synthesis phase. If the cell is not big enough or not ready to go onto the next phase, they enter the G0 phase as you can see on the diagram. In G0, the cell is in a resting phase until it is ready to move on. 

At the G2 checkpoint, there is a DNA synthesis checkpoint during the S phase. Here, there is a check to make sure that the DNA has been replicated correctly. If the DNA is replicated correctly, it moves on to the M (Mitosis) phase. 

The final checkpoint is the metaphase checkpoint. This occurs in the (M) Mitosis phase and checks whether metaphase is complete. If it is complete, the cell divides and the process repeats.

Cancerous Cells

However, disruptions in the cell cycle can lead to cancerous cells. Cancerous cells are cells that are unregulated and divide uncontrollably. Cancerous cells have the ability to migrate or metastasize to other regions of the body that they didn’t originate in.

Apoptosis

Apoptosis is programmed cell death. Apoptosis is a normal and controlled process within multicellular organisms. It is very important because it maintains the balance of cells within an organism. 

For example, apoptosis can occur during the development of new cells. If these cells are not divided correctly, they could lead to cancer or a virus. Without apoptosis, these harmful cells could continue dividing and multiplying which could cause an adverse effect on the organism. Apoptosis is very important because if damaged or mutated cells do not get the signal to go through apoptosis, cancer can form.

Image courtesy of Giphy.

Watch AP Bio live streams here.

Resources: