The cell cycle is the time from one cell division to the next. It passes in two consecutive stages - interphase and the actual division. The duration of this process is different and depends on the type of cells.
Interphase is the period between two cell divisions, the time from the last division to cell death or loss of ability to divide.
In this period, the cell grows and doubles its DNA, as well as mitochondria and plastids. In the interphase, protein and other organic compounds are synthesized . The most intensive synthesis process takes place in the synthetic period of interphase. At this time, nuclear chromatids are doubled, energy is accumulated, which will be used during fission. The number of cellular organelles and centrioles is also increasing.
Interphase occupies almost 90% of the cell cycle. After it passes mitosis, which is the main way of dividing eukaryotic cells (organisms whose cells contain a formed nucleus).
During mitosis, the chromosomes become denser, and a special apparatus is also formed, which is responsible for the even distribution of hereditary information between the cells that are formed as a result of this process.
Cell division takes place in several stages. The stages of mitosis are characterized by individual characteristics and a certain duration.
Mitosis phases
In mitotic cell division, the corresponding phases of mitosis pass: prophase, after it comes metaphase, anaphase, telophase is the final one.
Phases of mitosis are characterized by the following features:
- prophase - the nuclear membrane disappears. In this phase, centrioles diverge to the poles of the cell, and the chromosomes condense (condense);
- metaphase - characterized by the placement of maximally compacted chromosomes, which consist of two chromatids, at the equator (in the middle) of the cell. This phenomenon is called metaphase plate. It is in this period that chromosomes can be well examined under a microscope. In the metaphase of mitosis, some ends of the fission spindle threads also attach to the centromeres of chromosomes, and the other ends to centrioles.
- anaphase - in this period there is a separation of chromosomes into chromatids (they diverge to different poles). In this case, chromatids become separate chromosomes, which consist of only one chromatid strand;
- telophase - characterized by decondensation of chromosomes and the formation of a new nuclear envelope around each chromosome. The threads of the fission spindle disappear, nucleoli appear in the nucleus. Cytotomy also takes place in the telophase, which is the separation of the cytoplasm between daughter cells. This process in animals is carried out due to a special division groove (constriction, which divides the cell in half). In plant cells, the cytotomy process is provided by a cell plate with the participation of the Golgi complex.
What is the biological significance of the mitosis process?
Phases of mitosis contribute to the accurate transmission of hereditary information to daughter cells, regardless of the number of divisions. At the same time, each of them receives 1 chromatid, which helps to maintain a constant number of chromosomes in all cells that are formed as a result of division. It is mitosis that provides the transmission of a sustainable set of genetic material.