Mitosis Cell Division: Definition, Stages and Diagram

Mitosis cell division is the process by which a cell replicates and divides producing two identical daughter cells. Through mitosis, the cell maintains a constant number of chromosomes during cell division. The mitosis cell division occurs in somatic cells.

The process of mitosis cell division plays an important role in all living organisms. 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. In this article, we will cover the mitosis cell division diagram, structure, and function.

What is Mitosis?

Mitosis cell division is a process that occurs during cell cycle where chromosomes are replicated and separate into two new identical nuclei. It 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 and ends with the division of the cytoplasm (cytokinesis). Mitotic division has following phases:  

• Prophase
• Metaphase
• Anaphase
• Telophase

What are the Key Features of Cell Division by Mitosis?

Following are some of the features of Mitosis:

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

What are the Stages of Mitosis?

The mitosis cell division stages are as follows:

Interphase of Mitosis

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

• G1 Phase: In this, the cell starts to prepare proteins necessary for cell division.
• S Phase: S phase is also known as the synthetic phase. Here, DNA replication takes place.
• G2 Phase: DNA Replication ends and the cell enters into the M phase.

After completing the G2 phase, the cell enters the M (or mitosis) phase which starts from Prophase.

Prophase of Mitosis

Prophase is the first stage in the process of mitosis cell division. The characteristics of prophase of mitosis are discussed below.

• The prophase of mitosis is the first stage
• 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 starts 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

• It is the second phase of mitosis where the nuclear envelope starts breaking down into "membrane vesicles", 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 of Mitosis

The next stage is the Metaphase. Following are some of its features:

• 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 kinetochore, which helps in the attachment of spindle fibers to the chromosomes. 

Anaphase of Mitosis

Next stage of mitosis is Anaphase. The following events occur during 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 of Mitosis

The next phase is the Telophase. The following events occur during 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 reappearing. 

Cytokinesis 

Cytokinesis is the process in cell division which divides the cytoplasm of the parent cell 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. 

What is the Function of Mitosis Cell Division?

The main functions of mitosis are listed below:

• Mitosis cell division helps in cell development
• In unicellular organisms, mitosis is the process used for Asexual reproduction.
• It helps in the replacement of damaged cells with new ones.

Importance of Mitosis Cell Division

The significance of process of mitosis is:

• Mitosis 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. 
• It helps in cell repair by dividing the cell to restore the nucleo-cytoplasmic ratio of the cell which is disturbed by cell growth. 
• The mitosis cell division 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. 

Mitosis Cell Division in Onion Root Tip

In onion root tips, mitosis cell division is clearly notable as these regions contain actively dividing cells responsible for root growth and development. The cells in the root tip undergo mitosis to produce new cells for root elongation, allowing the plant to explore and attach itself in the soil. The observation of mitosis in onion root tips is a common practical experiment in biology syllabus as it gives students a firsthand understanding of cell division and its significance in plant growth.

Mitosis and Meiosis Difference

There are various difference between mitosis and meiosis. The mitosis vs meiosis is given below:

Also Read: Difference Between Mitosis And Meiosis

Conclusion - Mitosis Cell Division - Definition, Stages and Diagram

Mitosis is the division of parent cell into two identical daughter cells. Mitosis is also called equational division because the number of chromosomes remain the same in the daughter cells. Mitosis is useful in repairing damaged tissue and increase the size of organism. Mitosis phases are prophase, metaphase, anaphase, and telophase.

Also Read

• Cell Division - Mitosis and Meiosis
• Meiosis - Definition, Stages, Function and Purpose
• Difference Between Mitosis And Meiosis