In the process of reproductive functions of living organisms, cell division occurs . Mitosis is the most common way to reproduce eukaryotic cells through their indirect division. Its biological role consists in the uniform distribution of chromosomes between subsequent daughter nuclei, which guarantees the formation of an identical genetic type of cells and ensures the preservation of heredity in the line of subsequent generations of cells.
What is mitosis? It is a fundamental process of the individual development of an organism and its successive transformations in relation to morphological, physiological and biochemical, which, in aggregate, constitutes ontogenesis. Due to myotic division, the number of plant cell populations increases. The division of a fertilized egg and the progress of the bulk of animal tissue occurs according to the same principle.
The stages of myotic division
Duration of mitosis in tissues of animal origin lasts up to 60 minutes, in plant tissues - up to 3 hours. Mitosis and its phases, based on morphological properties, it is conventionally divided into 5 periods, which allow to establish thoroughly what mitosis is:
1. Prophase - stage of myotic division, characterizing the spiral of chromosomes from two similar chromatids with the subsequent formation of the mitosis apparatus.
2. Prometaphase - a period of rapid decay of the nuclear membrane into small parts identical to the endoplasmic reticulum.
3. Metaphase - a long stage of myotic cell division, consisting of two periods: metakinesis - concentration of chromosomes in the region of the spindle of division in the form of an equatorial plate - and separation of chromosomes into chromatids.
4. Anaphase is a fast fission phase during which chromatids are separated and distributed at opposite poles. It only takes a few minutes.
5. Telophase - the final stage of mitosis, during which the movement of chromosomes ceases, the myotic apparatus is destroyed, daughter nucleoli are formed, the nuclear membrane is formed and the cell body is divided into two independent units.
Types of mitosis
What is mitosis and what is its classification? This can be more accurately established by determining its types. Given the unique specificity of mitosis, which manifests itself in different groups of division, certain types of its systematization applicable to one taxon are not comparable with others. One of the main features used in the formation of the typology is the characteristic action of the nuclear membrane, regarding the behavior of which three types of mitosis are shared:
1. Closed mitosis is characterized by the fact that spindle formation and subsequent fission occurs inside the nucleus without destroying its shell.
2. Open mitosis is determined by the decay of the nuclear membrane during cell division.
3. Half-closed mitosis. What is mitosis of this type can be determined by the collapse of the membrane exclusively at the poles of the myotic spindle, with the subsequent formation of “polarity windows”.
Another defining sign of the type of mitosis is the type of symmetry of the spindle. Regarding this characteristic, fundamental concepts share the following concepts:
- pleuromitosis (when the spindle symmetrically or asymmetrically consists of two parts);
- orthomitosis (when bipolar symmetry of the spindle is detected, and in the metaphase stage an equatorial plate is formed).
The value of mitosis
In the process of mitosis, identical reproduction of cells occurs. It is an essential tool for preserving the chromosome set. The main role of mitosis is to copy genetic information. This process affects growth and development, cell movement, regeneration and asexual reproduction.