THEmitosisit is a type of cell division that occurs in all eukaryotic cells and ensures the formation of two daughter cells. It is an important process for the growth and regeneration of multicellular organisms and for the asexual reproduction of unicellular organisms.
Despite being a continuous process, mitosis can be divided into four distinct phases: prophase, metaphase, anaphase and telophase. This process starts after the interphase period, which comprises the moment between two phases of cell division.
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In the interphase phase, the cell is not dividing, however, there is intense activity to prepare for the beginning of cell division. This period can be divided into three stages:
G1 (G refers to the word gap, which means interval): In G1, the RNA transcription and the protein synthesis, processes that normally take place in the cell. During this period, there is also a gradual increase in the cell, which is small after the cell division process.
s (S refers to the word synthesis
, which means interval): In S, replication occurs (duplication) of the DNA, being, therefore, an important step to ensure the maintenance of the amount of chromosomes after cell division. At this stage, the duplication of the centrioles also occurs.G2: the cell makes sure that the DNA is replicated and grows a little more in size. In this phase, the production of RNA is also restarted.
It is important to note that cells that will not start a new division enter a phase known as G0.
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→ phases of mitosis
As stated earlier, mitosis is a process that gives rise to two daughter cells with the same number of chromosomes as observed in the mother cell. This process is didactically divided into four basic steps:
Prophase: In this stage, which is the longest in mitosis, there is DNA condensation that was duplicated in the interphase period. The membrane surrounding the nucleus becomes disorganized and forms vesicles that remain in the cytoplasm until the end of mitosis, at which point the nuclear envelope is rebuilt. A pair of centrioles migrates to each pole of the cell and microtubules appear between them, initiating the formation of the mitotic spindle. At this stage the nucleolus also disintegrates.
Metaphase: At this stage of mitosis, chromosomes migrate to the equatorial plane of the cell. Each chromosome has two chromatids, which attach to the microtubule through a region called the kinetochore. At this stage, the chromosomes reach their greatest degree of compaction.
Anaphase: the chromosomes separate, and each chromatid moves towards the pole of the cell. This migration occurs due to the shortening of the spindle fibers.
Telophase: there is reconstruction of nuclear envelopes, decondensation of chromosomes and reconstruction of the nucleolus.
From the end of anaphase to the end of telophase, the cytokinesis process is observed. This process consists of the division of the cytoplasm and the formation of two daughter cells.
ATTENTION: Some authors also consider a phase known as prometaphase, an intermediate phase that occurs between prophase and metaphase.
By Ma. Vanessa dos Santos
Would you like to reference this text in a school or academic work? Look:
SANTOS, Vanessa Sardinha dos. "What is mitosis?"; Brazil School. Available in: https://brasilescola.uol.com.br/o-que-e/biologia/o-que-e-mitose.htm. Accessed on June 28, 2021.