Cell cycle - the time from one cell division to the next. It takes place in two successive stages - interphase and division itself. 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 until cell death or loss of the ability to divide.
In this period, the cell grows and doubles its DNA, as well as mitochondria and plastids. In the interphase, the synthesis of protein and other organic compounds takes place. The synthesis process is most intense in the synthetic period of the interphase. At this time, nuclear chromatids double, energy is accumulated, which will be used during division. The number of cell organelles and centrioles also increases.
Interphase takes up almost 90% of the cell cycle. After it, mitosis takes place, which is the main method of cell division in eukaryotes (organisms whose cells contain a formed nucleus).
During mitosis, the chromosomes are compacted, and a special apparatus is formed, which is responsible for the uniform distribution of the hereditaryinformation between 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
During mitotic cell division, the corresponding phases of mitosis pass: prophase, after it comes metaphase, anaphase, the final one is telophase.
The phases of mitosis are characterized by the following features:
- prophase - the nuclear envelope disappears. In this phase, the centrioles diverge towards the poles of the cell, and the chromosomes condense (compact);
- metaphase - characterized by the placement of the most compacted chromosomes, which consist of two chromatids, at the equator (in the middle) of the cell. This phenomenon is called the metaphase plate. It is in this period that chromosomes can be clearly seen under a microscope. In the metaphase of mitosis, some ends of the spindle fibers are also attached to the centromeres of the chromosomes, and the other ends to the centrioles.
- anaphase - in this period, the chromosomes are divided into chromatids (they diverge to different poles). In this case, the chromatids become separate chromosomes, which consist of only one chromatid strand;
- telophase - characterized by decondensation of chromosomes and the formation of a new nuclear membrane around each chromosome. The fission spindle threads disappear, and nucleoli appear in the nucleus. In telophase, cytotomy also takes place, which isdivision of the cytoplasm between daughter cells. This process in animals is carried out due to a special fission furrow (a constriction that divides the cell in half). In plant cells, the process of cytotomy is provided by the cell plate with the participation of the Golgi complex.
What is the biological significance of the process of mitosis?
The 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 the constancy of the number of chromosomes in all cells that are formed as a result of division. It is mitosis that ensures the transfer of a stable set of genetic material.
