The cell cycle, also known as the cell-division cycle, is the process by which a cell goes through the sequence of events that leads to its division into two daughter cells. These activities include the duplication of its DNA (also known as DNA replication) and some of its organelles, and then following that, the partitioning of its cytoplasm and other components into two daughter cells through a process known as cell division.

The Management of the Cell Cycle

How is it that the cell is able to determine when it should divide? How does the cell determine when it is the appropriate time to copy its DNA? How does the cell know whether or not it should go through mitosis or cytokinesis at a certain point? These issues can be answered by looking at the mechanisms that are used to govern the cell cycle. But what exactly is it that controls or regulates the cell cycle? The processes involved in the regulation of the cell cycle are essential to the continued existence of a cell. The identification and repair of any damage to the DNA, as well as the suppression of unchecked cell proliferation, are all examples of these processes. It is essential for the life of an organism to prevent uncontrolled cell division, which can be lethal to the organism.

Cyclins, in addition to Kinases

A multitude of protein-controlled feedback systems are responsible for the regulation of the cell cycle. Kinases and cyclins are examples of different classes of proteins that have a role in the regulation of the cell cycle. By binding to kinases, cyclins trigger the activation of certain kinases; more specifically, they trigger the activation of cyclin-dependent kinases (CDK). Cyclins are a group of proteins that are rapidly produced at critical stages in the cell cycle. Cyclins are responsible for many cellular processes. CDKs are enzymes that, after being activated by cyclins, phosphorylate other target molecules in order to either activate or deactivate them. The progression through the cell cycle is initiated by the precise regulation of proteins in the cellular environment. Because of their groundbreaking work in identifying these essential proteins, Leland H. Hartwell, R. Timothy Hunt, and Paul M. Nurse were awarded the Nobel Prize in Physiology or Medicine in 2001.

Cyclin-Dependent Kinases

The cyclin-dependent kinases, also known as CDKs, are a family of protein kinases that were initially identified due to the function that they play in controlling the cell cycle. CDKs are found in all eukaryotic organisms, and their role as regulators in the cell cycle has remained mostly unchanged throughout the course of evolution. CDKs are relatively simple proteins that consist of little more than the kinase domain in their structure. A cyclin-dependent kinase (CDK) binds to a cyclin regulatory protein, which in turn activates the protein. If a CDK does not bind to cyclin, its kinase activity is significantly reduced. CDKs are considered to be serine-threonine kinases since they phosphorylate their substrates on serine and threonine residues. In addition to their role in transcription regulation, CDKs are also involved in the processing of mRNA and the differentiation of nerve cells.

Checkpoints

• There are critical checkpoints during the cell cycle. The cell is able to move on to the subsequent phase of the cell cycle once it has obtained the necessary signals or information through the process of feedback regulation. Signals can also be received by the cell that inhibit its progression to the subsequent phase of the cell cycle. Because of these signals, the cell is able to finish the previous phase before going on to the next one. The checkpoint for cell growth (G1), the checkpoint for cell division (G2), and the checkpoint for mitosis are three important checkpoints. Another checkpoint is located during the process of DNA synthesis
• The cell growth (G1) checkpoint is responsible for determining whether or not the cell will enter the S phase of the cell cycle and continue on to divide, whether or not it will delay division, or whether or not it will enter a stage of rest. The G1 phase is where the cell will spend the majority of its time during the cycle. G1 is the region of the cell where the bulk of the cell’s work gets done. Key proteins will signal the cell to proceed to the S phase and stimulate the beginning of DNA replication if the cell has completed its functions and has grown to a size significant enough to be divided in half. This will happen if the cell has grown to a size significant enough to be divided in half. If the cells are not going to divide, as is the case with certain muscle and nerve cells, the cell will pause at this checkpoint and proceed to the G0 phase, which is the period of rest. It’s possible that some cells will never divide and will always remain in this resting phase forever
• At the conclusion of the G2 phase is where the second checkpoint can be found. Once you pass this checkpoint, the mitotic process will begin in earnest. In the event that this checkpoint is successfully traversed, the cell will start the myriad of chemical events that herald the start of mitosis
• The mitotic checkpoint marks the completion of one cycle and the start of the next one. This checkpoint happens at the point in metaphase where all of the chromosomes should have aligned at the metaphase plate. It is also known as the metaphase plate alignment checkpoint. This checkpoint denotes the beginning of anaphase, which enables the cell to finish mitosis and get ready for the G1 phase of the subsequent cell cycle
• The DNA synthesis (S) checkpoint is responsible for determining whether or not the cell is prepared to undergo mitosis. At this stage, DNA repair enzymes perform quality assurance checks on the copied DNA. In the event that the checkpoint is successfully traversed, the myriad of molecular mechanisms and processes necessary for mitosis will start

Conclusion 

Cell survival depends on cell cycle regulation. These include DNA repair and preventing uncontrolled cell division. Uncontrolled cell division is dangerous; preventing it is vital to survival.When does the cell divide? When does a cell copy DNA? How does a cell know when to undergo mitosis or cytokinesis? These questions can be answered by examining cell cycle mechanics. What governs the cell cycle? Cell survival depends on activities that regulate the cell cycle. These procedures include identifying and repairing DNA damage and suppressing unregulated cell proliferation. Uncontrolled cell division can be fatal to an organism.