- What is the cell cycle?
- Cell cycle phases
- Cell cycle regulation
- Cell cycle checkpoints
- Importance of the cell cycle
- Cancer and the cell cycle
We explain what the cell cycle is, its phases, control points and regulation. In addition, its implication in the development of cancer.
What is the cell cycle?
The cell cycle is the ordered and sequential set of events that take place within all cells in general. They involve their growth and eventual reproduction in two cells "daughters". This process is essential for the existence of the multicellular beings.
It begins with the appearance of a young cell and ends with its maturation and cell division, that is, the creation of two new cells. It is performed according to a set of stimuli and biochemical responses interpreted by the cell nucleus, which guarantee the orderly reproduction of body tissues.
For this reason, cells normally start their cell cycle when environmental conditions are conducive to it. However, the cycle does not always occur in the same way, with important cell variations animals Y vegetables or prokaryotes Y eukaryotes. However, it occurs in all living beings, with similar purposes and similar stages.
Cell cycle phases
The stages of the cell cycle are described according to the formula:
- G1. From English Gap 1 or Interval 1
- S. Synthesis or Synthesis
- G2. Gap 2 or Interval 2
- M. M-phase or Phase M, whose name is due to the fact that it comprises the mitosis or meiosis, before cytoplasmic division or cytokinesis.
Before starting the cell cycle, cells are called "quiescent" (meaning that they choose to be still), and once they have started the cell cycle, they are called "proliferating" (meaning that they multiply rapidly).
The cell cycle is not linear, but circular, as young cells can choose to repeat the process, thus originating two new ones each, as dictated by the needs. And broadly speaking, the different stages that comprise it are organized based on two separate phases, which are:
- The interface. This first phase comprises the G1-S-G2 stages, and during them it grows to its adequate level to start the doubling of its genetic material, copying it completely according to your DNA.
- Stage Gap 1. The cell physically grows, duplicating its organelles and the proteins necessary for the following stages.
- Stage S. A complete copy of the cell's DNA is synthesized, as well as a duplicate of the centrosome, which will help separate the DNA in later stages.
- Gap stage 2. The cell grows even larger in size, generates protein and new organelles and prepares for mitosis, cell division.
- The M phase. The mitotic phase begins when the cell has already duplicated its genetic material and organelles, ready to divide into two identical individuals. The onset of mitosis starts from the separation of DNA into two double strands, and the two new cell nuclei move away from each other, towards opposite poles.
The M phase is divided into four distinct phases: prophase, metaphase, anaphase, telophase.
Thus, when cytokinesis begins, which is the preparation for the definitive separation of the two new cells, each nucleus is left separately. A barrier begins to be generated between both cells, which will later become part of the cell itself. plasma membrane, and finally physical separation occurs.
Cell cycle regulation
The cell cycle must occur under very specific conditions, which merit very specific instances of control and regulation. So without the precise instructions, not only does the entire cycle not start, but there will be no transition from one stage to the next.
In the first instance, control is exercised by the genes on own genetic code of the cell. There are the instructions for making or modifying proteins to trigger each stage of the cycle. The set of enzymes that activate, facilitate or terminate each phase are cyclins and cyclin-dependent kinases.
Cell cycle checkpoints
There are, especially during mitosis, a series of checkpoints in the cell cycle, where the process is monitored and it is ensured that no mistakes have been made. These are transitory existence verification routes, that is, once they have fulfilled their function and verified that the process continues without failures, they disappear.
In addition, if the problem, after a period of time, has not been resolved satisfactorily, these checkpoints prepare the cell to undertake self-destruction or apoptosis.
The checkpoints during mitosis are:
- At the end of the G1 stage and before the S. This is the checkpoint for non-replicated DNA, which inhibits the Cdc25 gene, which in turn activates Cyclin A / B Cdk1. Thus, it prevents the cycle from continuing.
- Before anaphase in mitosis. It is a control point that guarantees the separation of chromosomes, and operates by activating the Mad2 protein that prevents the degradation of segurin, until the conditions are appropriate.
- DNA damage checkpoints in G1, S or G2. In the event of cellular damage, specifically to the genetic material, the p53 protein will be activated, which allows DNA repair. Should this fail, apoptosis processes are immediately activated.
Importance of the cell cycle
The cell cycle is the fundamental cycle of reproduction of cells, which allows the growth of multicellular organisms and the repair of tissues. In addition, it causes the necessary proliferation to, for example, generate the critical cell mass to form embryos of future new individuals of the species.
It is a process that is carried out constantly. It is encoded in our DNA itself, so it is one of the fundamental and original cycles of eukaryotic cell life.
Cancer and the cell cycle
As is known, cancer is a disease in which certain cells of certain tissues initiate an abnormal, unstoppable reproduction of dysfunctional cells. This process, which may well cause death if not stopped in time, is not interrupted by the natural process of cellular apoptosis, thus requiring medical intervention.
Many specialists suggest that the initiation of the carcinogenic process is in certain cell cycle regulatory genes that do not work well or have been damaged, subjecting the process to a lack of control that in turn generates other failures and culminates in the formation of a tumor. These genes are known as oncogenes, and their precursors as protoncogenes.