Division is an important property of cells. Without this process, it is impossible to imagine an increase in the number of various microorganisms or unicellular creatures. In addition, it provides restoration of tissues and even entire organs of multicellular organisms.
It is worth noting that the totality of processes that take place between two divisions is called the cell cycle. It goes through in stages. Thus, interphase and the actual mitotic cycle are characteristic, in which the cell divides.
In order to preserve the appropriate amount of genetic material, DNA molecules are duplicated. In addition, protein biosynthesis takes place in the interphase, as well as the formation of important cell structures.
I must say that the interphase is longer than the division itself. It consists of the following steps:
• Presynthetic period - characterized by active growth processes, synthesis of proteins and nucleic acids, as well as the formation of specific activators of the synthetic period. The cell reaches normal size and restores the organelles necessary for functioning. The duration of this period is several hours or days.
• Synthetic period - characterized by DNA replication and the synthesis of histones, which are responsible for the nucleosomal packaging of newly synthesized nucleic acids, as well as for the doubling of chromosomes and centrioles. The duration of this period is up to 12 hours.
• Postsynthetic period - lasts until mitosis, is characterized by the accumulation of energy and the synthesis of tubulin protein, which is necessary for cell division. This period ends in 2-4 hours.
After interphase, the stage of mitosis takes place, which is also characterized by certain sequential processes during which daughter cells with a well-defined set of chromosomes are formed.
It is worth noting that the reasons for the termination of the fission process remain unknown to this day. The mechanism that provokes its renewal is also unknown, although hormones have been established, under the action of which the mitotic cycle is activated. The factors that control cell population size are also not fully understood.
Glucocorticoids affect the mitotic cycle of cells. Prolactin, thyrotropin, estrogens and androgens are also able to influence cell division in target tissues in a certain way.
It is worth noting the following feature of benign tumors - their cells are characterized by a circadian mitotic cycle (daily). It is assumed that with the progression of the tumor, there is a decrease in the body's sensitivity to the so-called. keylonam - inhibitor cells.
The division and size of the cell population is also influenced by the activity of lysosomalapparatus, since its enzymes can be destructive.
It must be said that the process of formation of new cells depends on the type of tissues, the influence of external factors and the physiological state of the body, therefore, in some cases, it may have certain individual characteristics, be characterized by further growth of the cell population or the termination of this process.
