In this video, we're going to introduce the cell cycle checkpoints. Recall from our last lesson video that these cell cycle checkpoints are very important for controlling or regulating the cell cycle. They ensure that errors do not accumulate and that the cell does not prematurely enter the next phase of the cell cycle. Cell cycle checkpoints act like stop signs where the cell can stop and make sure everything is okay before it moves on to the next phase. We're going to talk about 4 major checkpoints that control the progress of the cell cycle.
Take a look at our image down below, showing the cell cycle from our previous lesson videos. Notice that we've included the 4 major checkpoints, acting like stop signs throughout the cell cycle, where the cell will literally stop at each of these checkpoints to make sure that everything is okay before it proceeds to the next phase. At each of these checkpoints, there are specific events that occur. It's important to note that these events don't need to be memorized if you understand the cell cycle itself.
The first checkpoint we're going to discuss is the G1 checkpoint, which occurs right at the end of the G1 phase of interphase. The G1 checkpoint acts like a stop sign for the cell, ensuring everything is okay before it proceeds. Before DNA gets replicated in the S phase, the cell checks for any errors in the DNA and fixes them if necessary.
After the S phase, where the DNA and the centrosome are replicated, comes our second checkpoint, the S checkpoint. Here, the cell confirms the proper replication of DNA and attempts to fix any errors that may have occurred.
Next is the G2 checkpoint, which comes at the end of the G2 phase, just before the M phase, mitosis. At the G2 checkpoint, the cell ensures that all enzymes and proteins needed for mitosis and cytokinesis are available. If they are not, the cell will stop at this checkpoint to make sure that they are made available.
Finally, we have the M checkpoint, which occurs at metaphase. During the M checkpoint, the cell confirms that all chromosomes have aligned properly in the middle of the cell and that spindle fibers are attached properly. This checkpoint helps prevent unregulated cell cycle progression which can lead to cancer. These checkpoints are crucial to ensure the cell cycle is under control and that cell division occurs only when it's supposed to and properly.
This concludes our introduction to the 4 cell cycle checkpoints. We'll get some practice applying these concepts as we move forward in our course. I'll see you all in our next video.