Mitosis: Definition, Features, Stages and Importance

Mitosis is a process of cell division in which two daughter cells are produced from a single parent cell. This process occurs in eukaryotic single-celled organisms. Cell division results in the formation of genetically identical cells with the same number of chromosomes. Mitosis is a process of asexual reproduction and is also known as equational division. 

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What is Mitosis? 

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The process in which a chromosome replicates into two daughter nuclei is called mitosis cell division. This process occurs in the human body and helps in the growth and development. Throughout the lifetime, this process replaces old cells with new ones.

• Mitotis begins with the separation of the cell nucleus and this process is called karyokinesis.
• The cytokinesis occurs at the end of the mitosis stage which involves the separation of cytoplasm.
• Two daughter cells are produced from the division of a single parent cell.
• Cell division by mitosis is also called equational division as the daughter cells share equal amounts of genetic material. 
• Every daughter cell produced must have a complete set of chromosomes.
• An incomplete set of chromosomes leads to abnormalities causing genetic disorders.

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Features of Mitosis

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The following are the features of mitosis:

• Two identical daughter cells are formed from the parent cell in every cell division cycle.
• This process of cell division is called equational division as the chromosome numbers in parent and daughter cells are equal.
• The growth of vegetative parts of the plants like roots, stems, leaves etc is through mitosis. 
• There is no occurrence of segregation and combination. 

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Stages of Mitosis

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Mitosis begins initially from the prophase, but the cell spends most of its time in the interphase so as to prepare itself for division. The 4 stages of mitosis are namely:

1. Prophase
2. Metaphase
3. Anaphase
4. Telophase 

Interphase

The interphase is the stage where the cell obtains its nutrients. This phase is also called the metabolic phase and is further divided into the G1, S and the G2 sub-phases

• The stage that occurs before the synthesis of DNA is called the G1 phase.
• The S phase is the stage at which DNA replication takes place
• G2 is the final stage that occurs when DNA synthesis has ended and prophase has started.

Prophase

After the G2 stage of interphase, the prophase begins. During this phase, the genetic material condenses into a compact form.

• The chromosome looks like a thin, uncoiled thread during the early prophase and becomes coiled, short, and more distinguishable, during mid-prophase.
• At the time of late prophase the chromosomes appear thick, short, and more prominent. 
• Two chromatids of each chromosome attached to the centromere are visible.
• At the end of prophase mitotic spindle, microtubules, and proteinaceous components of cytoplasm begin to assemble.

Prophase

Metaphase

Followed by the prophase starts the metaphase. The microtubules at this stage pull the chromosomes and they appear to be seen in the centre of the cell.

• This is called the metaphase plate.
• This is the stage where the chromosomes can be seen under a microscope.

Metaphase

Anaphase

Anaphase is the third stage of mitosis. The chromatids split at the centromere during anaphase and begins to travel towards the poles.

• Each chromatid of the chromosome is free at the centromere and is connected to a spindle tube.
• The chromatids then begin to separate and each one of them moves to the opposite poles.
• Each of the chromatids becomes a chromosome after the separation.

Anaphase

Telophase

The final stage i.e. the telophase starts when the chromosomes reach the pole. During this phase, the genetic material is distributed to the daughter cells.

• The chromosomes which were present at each pole come together to form a mass or cluster. 
• This happens when the nuclear membrane starts forming around it.
• The nucleolus, Golgi bodies, and endoplasmic reticulum that vanished in the prophase reappear.
• telophase is followed by cytokinesis, where the cytoplasm is divided to form two daughter cells. 

Telophase

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Functions of Mitosis

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There are several functions of mitosis, a few of which are mentioned below:

• Mitosis cell division helps in replacing worn-out cells with new ones. For example, in the case of skin cells.
• In unicellular organisms, mitosis is the asexual mode of reproduction. For example, yeast and amoeba reproduce via this method.
• It functions in developing two identical daughter cells.

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Importance of Mitosis

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In our previous sections, we have read how mitosis helps in distributing equal amounts of genetic material to each cell, apart from this there are other importance of mitosis such as:

• This process helps in the development and growth of multicellular organisms.
• The skin, blood and tissue cells are maintained via this process.
• It helps in the growth and maturation of embryos.
• It helps in repairing damagestissues and organs.
• Maintainenece of chromosomal number.

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Things to Remember 

• .The division of the mother cell into two identical daughter cells is called mitosis.
• Prophase, prometaphase, metaphase, anaphase, and telophase are the stages of cell division.
• The point where spindle fibres to the centromere is called a kinetochore. 
• During prophase, the nucleolus, nuclear membrane, and organelles disappear. 
• The chromatids split at the centromere during anaphase.