Mitosis

Mitosis is one of the phases of the cell cycle. In mitosis, the mother cell is divided into the daughter cell. In mitosis cell division and cytokinesis take place. The cell cycle is divided into two parts i.e., the Interphase and M phase. M phase is known as mitosis and cytokinesis. 

The cell cycle is an important phenomenon in all living organisms. During cell division, a cell divides and produces new cells through the process of DNA replication. The duration of the cell cycle varies from organism to organism.  In animal cells, mitosis takes place in the diploid (2n) somatic cells; while in plants, it takes place in both haploid (n) and diploid (2n) cells. 

What is Mitosis?

Mitosis is also known as the Equational division, as during this phase the number of chromosomes in the parent and daughter cells remains the same. During this phase, the actual division of the cell takes place. It starts with the nuclear division (karyokinesis) in which the division of the nucleus and separation of the daughter chromosomes takes place; & ends with the division of the cytoplasm (cytokinesis). This phase is further divided into 4 phases, namely,  

• Prophase
• Metaphase
• Anaphase
• Telophase

Features of Mitosis

• Mitosis helps in replacing the damaged cell. The nearer cell start mitosis and if they don’t sense any neighbor cells.
• Mitosis help in the growth of the organism.
• The growth of vegetative parts in plants is done by mitosis.
• During mitosis segregation and combination don’t occur.

Stages of Mitosis

Cell Cycle M phase is further divided into different Stages. Following are the different stages of the cell cycle are:

Interphase

The cell cycle begins when the cell enters the interphase. Interphase is further divided into various stages those are:

1. G1 Phase: In this cell starts to prepare all the proteins which are necessary for cell division.
2. S Phase: S phase is also known as the synthetic phase. Here DNA replication takes place.
3. G2 Phase: Here DNA Replication ends and after this phase cell enters into the M phase.

After completing the G2 phase cell enters the M phase which starts from Prophase.

Prophase

• The first stage of mitosis is when the condensation of chromosomal material begins after G2 Phase ends, leading to untangling of chromosomal material. 
• The centriole begins to move towards opposite poles of the cell. 
• The mitotic spindle initiates to assemble which is helped by the microtubules. 
• Chromosomes seem to be composed of two chromatids attached to the centromere. 
• The nuclear envelope, Golgi bodies, endoplasmic reticulum, and nucleolus disappear. 

Prometaphase

Here the nuclear start degenerating, and microtubules start extending from the centromere to chromosomes. Microtubules are associated with the kinetochore which helps the chromosome to move inside the cell.

Metaphase

• Condensed chromosomes, which are now clearly visible in the microscope, spread in the cytoplasm because of the disintegration of the nuclear membrane and move to the center or the equator of the cell forming a plane of alignment of the chromosomes known as the metaphase plate.
• The chromosomes are made up of 2 sister chromatids which are attached by a centromere. Centromeres have a disc-shaped structure known as kinetochores, which help in the attachment of spindle fibers to the chromosomes. 

Anaphase

• Each chromosome starts to split simultaneously and forms two sister chromatids (chromosomes of future daughter nuclei). 
• These chromatids begin to move towards opposite poles.
• Centromeres which were at the poles until now, start to lead the way for chromatids toward the poles and begin to split. 

Telophase

• Chromosomes that have reached their respective poles start to decondense and cannot be seen individually anymore.
• The nuclear membrane, nucleolus, Golgi complex, and ER start appearing. 

Cytokinesis 

This is the phase in which the cell divides into two daughter cells. 

In animal cells, a furrow in the plasma membrane appears which gradually deepens and joins in the center dividing the cell cytoplasm into two.

• In a plant cell, due to the presence of a cell wall, a cell plate starts to form at the center of the cell which later forms a cell wall.
• Mitochondria, plastids, and other cell organelles get distributed between the two daughter cells. 
• In some organisms, the phenomenon of syncytium (multinucleate condition) takes place due to the absence of cytokinesis after karyokinesis. E.g., liquid endosperm in coconut. 

Function of Mitosis

The following is the function of mitosis:

• Mitosis helps in cell development
• In unicellular organisms, mitosis works like asexual reproduction.
• It helps the replacement of damaged cells with new ones.

Significance of Mitosis

• Restricted to diploid cells in higher organisms and haploid cells of some lower plants and some insects like male bees (drones), wasps, and ants. 
• Produces diploid daughter cells with identical genetic material.
• It helps in maintaining the chromosome number in each cell
• It helps in continuing the purity of the genome because no recombination and crossing over occurred.
• The growth of multicellular organisms depends on mitosis. 
• Helps in cell repair by dividing the cell to restore the nucleo-cytoplasmic ratio of the cell which is disturbed by cell growth. 
• Helps in the replacement of the cells of the upper epidermis, blood cells, and cells of the lining of the gut. 
• In plants, mitosis takes place in the apical and the lateral cambium which results in plant growth. 

FAQs on Mitosis

Question 1: What is Mitosis? 

Answer:

Mitosis is a part of the cell cycle, which helps a cell divide into two identical clones. 

Question 2: List all the stages of Mitosis.

Answer:

Mitosis includes the following stages, those are:

• Prophase
• Metaphase
• Anaphase
• Telophase

Question 3: Why is Mitosis called Equational Division? 

Answer:

Mitosis is known as the equational division because when the cell divides into two daughter cells, each of the daughter cells has the same number of chromosomes as the parental cell. 

Question 4: In what cells does Mitosis occur?

Answer:

The mitosis process is seen in eukaryotic cells. Early embryonic stages cell do mitosis faster than normal cells. 

Question 5: How are Mitosis and Meiosis different?

Answer:

Mitosis is an equational division, that occurs in each cell by which the mother cell divides into 2 cells. Whereas meiosis occurs in gametic cells i.e., sperm and egg cells.