Mitotic Cell Division Stages, Diagrams, & Summary (Explained!)

This article is about Mitosis Cell division and different stages of mitotic cell division.

Mitosis is an equatorial division in which a mother cell divides to form 2 daughter cells. This was first observed by a German biologist, Walter Flemming, in 1877 AD.

Mitosis takes place in vegetative or somatic cell. So, it is also called Somatic Cell Division.

In general, mitosis is preceded by the 5 stages of Interphase ( During which the DNA is replicated). Then, it is often followed by cytokinesis, which divides the cytoplasm, organelles, and cell membrane into 2 new cell containing roughly equal shares of these cellular components. We will discuss each of these stages in details below.

In mitotic cell division, the same number (diploid number) of chromosomes of the parent cell is maintained in each division of the cell. The cell division in which a diploid parent cell divides biologically into 2 diploid daughter cells is called mitotic cell division.

Let's get into mitosis cell division stages.

Interphase

Interphase is the non-dividing phase of Mitosis. In this phase, the actual cell division doesn’t occur. It is a phase of high metabolic activity, in which a cell makes all necessary preparations required for cell division. Interphase itself has is divided into 3 phases, namely G1 (first gap), S (synthesis), and G2(second gap).

During these 3 stages, the following activities take place:

• the cell grows by producing protein, and cytoplasmic organelles 
• Replication of DNA, and synthesis of histone protein take place which results in duplication of chromosomes
• Chromosomes are replicated only during the "S" phase

In animal cells, the centrosome begins to divide. Chromosomes appear in the form of diffused, long & coiled network called chromatin fibers.

Phases of Mitotic Cell Division

Mitosis is a continuous process. Mitosis cell division occurs in following 4 stages:
1) Prophase
2) Metaphase
3) Anaphase
4) Telophase

Prophase (pro = before, phasis = stage)

It is the first and longest stage of mitosis cell division. It lasts for 100 minutes. This stage involves a number of changes in the cell which take place simultaneously. In this stage, chromosomes are long, thin, and are like a thread. Each chromosomes has two chromatids. The two chromatids are joined at the centromere. The chromatin material condense into distinct thread like structure called a centromere and 2 sister chromatids which becomes shorter and thicker as the prophase proceeds. Nucleolus and nuclear membrane start disappearing towards the end of prophase. The two centrioles of the centrosome migrate towards opposite poles by forming spindle fibers.

Metaphase (meta = between, phasis = stage)

It is the second stage or middle stage of mitosis which lasts for 15 minutes. In this stage, nucleolus and nuclear membrane disappear completely and nuclear spindle appears. Chromosomes come to lie on equator and arms face towards poles. Spindle fibers attach themselves to centromere of chromosome whereas chromosomes becomes shorter and thicker due to condensation.

Anaphase (ana = back, phasis = stage)

It is the third and shorter stage of mitotic cell division. This stage last for 10 minutes. In this stage, centromeres of each pair of chromatids appear to repel each other and are separated forming two daughters chromosomes. Whereas, chromosomes migrate towards opposite poles due to the contraction of spindle fibers and repelling force of sister chromatids and becomes shorter and thicker, and take the shape of "U" ,"V" or "J" depending on the position of centromere.

Telophase (telo = end, phasis = stage)

It is the fourth and last stage of karyokinesis. During this stage, the events of prophase occurs in reverse sequence. It last for 60 minutes. The daughter chromosomes reach their respective poles, uncoil, and change into chromatin network. Nuclear membrane reappears around the chromatin network of each pole.

Therefore, two daughter nuclei with same number of chromosomes are formed.

Nucleolus appears in each daughter nucleus and spindle fibers disappear.

In animal cell, the centromere organizes itself above the nucleus at the end of karyokinesis.

At the end of telophase, karyokinesis is followed by cytokinesis. i.e - division of cytoplasm.

Cytokinesis (cyto = cell, kinesis= movement)

In this stage, the cytoplasm actually divides. In this stage, nuclear division occurs.

The process is slightly different between animals and plants cell.
In animal cells, there are actin filaments. These filaments interacts with each other causing the cell membrane to create cleavage furrow in them. The furrow then deepens, and eventually results in division of cell membrane to form two individual cells.

In plant cell, it has a rigid cell wall. Cytokinesis is accompanied by cell plate formation. In this process, a new cell plate is formed in the middle of the cell. This cell plate continues to grow so that it reaches the cell membrane and finally combines with the cell’s original plate. Now the newly formed plate breaks forming two individual cells.

Summary

Prophase

In brief the following things occur during prophase:

• DNA condenses to form chromosomes
• Nuclear membrane starts to fade Nucleolus disappears
• Centrioles start making spindle fires

Metaphase

• Chromosomes are joined by two spindle fibers
• Chromosomes arrange themselves at the equatorial plane
• Formation of equatorial phase occurs

Anaphase

• Spindle fibers shorten so that chromosomes pair separate and are taken towards each pole.

Telophase

• Separation of chromosomes complete in this phase
• In animals cell, cleavage furrowing occurs
• In plants cell, cell plate forms
• Reformation of nucleus and nucleolus Chromosomes uncoil