Definition
Definition
Mitosis is a process of cell division that allows two identical daughter cells to be produced from a parent cell. It is characterized by a set of four successive phases called:
- Prophase.
- Metaphase.
- Anaphase.
- Telophase.
Generalities
It is thanks to the mechanism of mitosis that the reproduction of a unicellular organism (comprising only one cell) is possible. Besides cell production, mitosis also ensures the growth of multicellular organisms , that is, organisms containing several cells.
History
The term mitosis was used by Schleicher in 1878, and by Flemming in 1882.
Classification
We distinguish:
- La meiosis which gives rise to different daughter cells, because they only contain half of the genetic heritage belonging to the mother cell. Meiosis only takes place within the reproductive cells of men and women, namely the testicles and the ovary. The sperm and the ova are the result of meiosis.
- La mitosis concerns all cells of the organism except reproductive cells. In other words, it is the set of physiological mechanisms of transformation and division of chromosomes, which allows the formation of two daughter cells from a mother cell, with the same number of chromosomes.
Symptoms
physiology
Meiosis is the succession of two mitoses :
- During the first cell division of meiosis, the number of chromosomes is the same in daughter cells as in the mother cell.
- In a second step, each of the two daughter cells divides, resulting in a stock of chromosomes separated into two.
In other words, the number of diploid cells decreases from four haploid cells to one chromosome. The meeting of an egg and a sperm at the time of fertilization results in a diploid cell.
Mitosis , in contrast , results in the formation of two daughter cells completely identical to the parent cell except for their size. It is identical in all living organisms and consists of four distinct phases:
- La prophase which includes a condensation followed by a duplication chromosomes inside the cell nucleus, ending with a disintegration of the nuclear envelope.
- La metaphase is essentially characterized by the constitution of the achromatic spindle in which, or more precisely along which, the chromosomes are arranged, ready to slide towards the poles at the time of prophase, the following episode.
- L'anaphase is characterized by the chromosome separation into two groups which will migrate towards the poles using the fibers of the spindle of the cell.
- La telophase constitutes the end of mitosis, where we see the appearance the formation of two cores new ones, and the separation of the mother cell resulting in two daughter cells, completely identical.