Cytokinesis is the process of eukaryotic cell division. Cytokinesis was one of the first cell cycle events to be observed using simple cellular biological techniques, however, the molecular characterization of cytokinesis has been slowed down by a particular resistance to in vitro biochemical approaches. While the outcome of cytokinesis is the same in all dividing cells, the mechanism of division varies across the different large eukaryotic kingdoms. For example, yeast and animals use a contractile ring that penetrates the middle of the cell to divide it while the cells build a new cell wall outward towards the cortex. As you might expect, there are some similarities in the molecules involved in cytokinesis in unicellular and animal cells, but at first glance, cytokinesis in plant and animal cells appears to be quite different. However, in recent years it has become clear that the basic processes are exactly the same in plant, protozoan, and animal cells.
One of a kindCytokinesis is mitosis, which is divided into several stages: prophase, metaphase, anaphase and telophase. Below are the features of each phase of cytokinesis.
Prophase
Prophase is marked by rapid biochemical changes, as a result of which the cell enters a state after which division begins directly. During prophase, the chromosomes assemble in the center of the cell and then duplicate, providing the genetic material for both newly formed daughter cells. Usually they are not visible under a microscope, but at that moment they become clearly visible under an optical microscope. Also at this time, the nucleolus disappears. By the middle of prophase, transcriptional activity stops completely. The structural features of cells are such that in the early stages of cytokinesis in cells with large chromosomes, it slows down and can stretch for several hours, while in the cells of creatures with small chromosomes (for example, mammals) it lasts about 15 minutes. After this time, the division of the body of the eukaryotic cell begins.
Metaphase
Metaphase of cytokinesis is the stage of cell division in which the chromosomes come out into the equatorial plane of the cell. Microtubules in this phase are updated especially actively. The chromosomes in the cell are arranged in such a way that it is convenient for the previously mentioned microtubules to attach to them. Sister chromatids separate but do not separate, stopped by centromeres. Due to the structural features of the cell, metaphase can be completedonly after the anaphase stimulation complex sends a signal to the cell. Thus, if the spindle is destroyed, the chromosomes will not be able to move to anaphase until the harmful effect is completely eliminated. This method of research is often used by geneticists in order to create cells that are in metaphase for hours, which are then used for research. The molecular mechanisms of this action still remain a mystery, but at the moment, scientists are successfully working on revealing their secrets.
Anaphase
Metaphase is followed by anaphase. For cytokinesis, this is both the most key and the shortest stage, during which sister chromatids diverge to the edges of the cell, forming daughter chromosomes. Although the anaphase is the shortest stage, it is subdivided into many phases. These stages are controlled by the previously mentioned anaphase stimulation complex. During anaphase, the chromosomes separate into two new cells. The chromatids of each chromosome are dispersed to opposite sides of the cells, forming two new daughter cells. Each side of the cell begins to have a complete set of chromosomes. Anaphase is important because it's what helps the DNA split in two, going to both sides of the cell. It ensures that the next gene can perform its function. If it doesn't, then there won't be two different DNAs for the next process
Telophase
Telophase is the final part of cell division. Its name comes from the Latin word telos,which means the end. At this stage, sister chromatids reach opposite poles. The small nuclear vesicles in the cell begin to rearrange themselves around the cluster of chromosomes at each end. As the nuclear envelope reforms by binding to chromosomes, two nuclei are created in one cell. Telophase is also marked by the dissolution of kinetochore microtubules and continued elongation of polar microtubules. As the nuclear envelopes transform, the chromosomes begin to decompose and become more scattered. After all processes are completed, the two new cells begin to function as if nothing had happened.
As we have seen, cytokinesis is a complex but at the same time understandable and fascinating process. Scientists are still studying the structural features of the cell.
