Mitosis

Explanation Of Mitosis

Mitosis is a process of cell division. Here the mother cell divides and produces two daughter cells. These daughter cells are identical to each other genetically. In the cell cycle, the division process is known as mitosis, where the DNA in the nucleus of the cell gets split into two equal chromosome sets.

The cell divisions that majorly happen in your body are because of mitosis. During the growth and development, an organism's body is populated with cells because of the process of mitosis. Throughout its entire life mitosis replaces any worn out and old cells and replaces it with new cells. For the organisms that are single-celled eukaryotes, the mitotic division is a reproduction form which adds new individuals to its population. This is the mitosis meaning.

The main aim of mitosis is to ensure that every daughter cell that gets formed is a full and perfect set of the chromosomes. If the cells have an excess or less number of chromosomes, then this does not function properly. They may either fail to survive or become cancerous. Here is the mitosis definition that you should understand.

During the mitosis stage, the cells do not just divide their DNA randomly, but instead, it gets split up in a series of steps that are well organised.


Mitosis – Its Features

  • Two daughter cells are formed from a mother cell in each mitotic cell division cycle of mitosis. This means that every nucleus divides in each cell cycle once.

  • The daughter cells resemble the mothers’ cell in size, shape and chromosome complement. 

  • The chromosome number is the same in the daughter and the mother cells, and this is what is known as equational or homotypic division.

  • Mitosis takes place in plants as well in its somatic organs. This is in its stem tip, root tip and leaf base. Mitosis in plants leads to the growth of its vegetative parts.

  • The entire mitosis process consists of just one equational or homotypic division.

  • During the mitosis stage, no recombination or segregation takes place.


The Different Stages Of Mitosis

The cell cycle refers to the period in which one cycle of the division of a cell gets completed. The cell cycle is divided into the interphase and the mitotic phase. 

The interphase is the stage of DNA synthesis, and the mitotic phase is the period where nuclear division takes place.

The time taken for the complete cell cycle varies from one species to another.


Interphase

The interphase is divided into the G1, S and the G2 sub-phases. G1 is the period of resting, S is the stage when DNA replication takes place, and G2 is again the stage of resting after the replication of DNA takes place.


Mitotic (M) Stages

What is mitosis? In the mitotic stages, the separation of the replicated DNA into two daughter nuclei takes place. It happens without any recombination. This means that the daughter nuclei will have the same combination of a chromosome as compared to the parent nucleus.

The M stage is further divided into prophase, metaphase, anaphase and telophase.

  • Prophase

The prophase begins after the G2 stage in interphase. In the early prophase stage, the chromosome looks like a thin and uncoiled thread. During the mid-prophase, the chromosome becomes coiled and short and also more distinct. In the late prophase stage, the chromosome will appear to be thick, short and more conspicuous as well as double longitudinally.

The two chromatids of every chromosome held at the centromere are visible centrally under a microscope. The nucleolus also becomes small in size. At the end of the prophase stage, the nucleolus and the nuclear membrane disappears.

  • Metaphase

Metaphase is the phase next to prophase. During this stage, the spindle tubes get formed, and the chromosome gets oriented in the centre at the equatorial plate. The chromosome gets attached at the centromere with a spindle tube. During the metaphase, the chromosomes can be seen clearly. Each chromosome's sister chromatids are joined with each other at the centromere; however their arms stay free.

  • Anaphase

During the anaphase, the chromatids get separated at the centromere. This starts to move towards the opposite side towards the poles. The chromatids in each chromosome are free at the centromere. However, each chromatid is attached to a spindle tube. The chromatids then start to move apart suddenly, and they move to one of the poles on each side. After the separation takes place, each of the chromatids turns into a chromosome.

  • Telophase

The chromosomes reach the pole and this is when the last stage or telophase begins. The spindle tubes start to disintegrate and this leads to a new membrane to be formed. This gets formed on each of the poles and it covers the chromosome. The nucleoli also appear at each of the poles.

Chromosomes again start to uncoil and unfold and it becomes thin and long. This starts to look like a single thread when seen under a light microscope. After this, the nucleus enters the interphase.

Among the four stages of mitosis, prophase takes the longest time.

The telophase is followed by cytokinesis, where the division of the cytoplasm takes place. The division in plants takes place due to a cell plate formation. In animals, the cytoplasm separation starts by the plasmalemma getting furrowed in the equatorial region, which results in the cytoplasm getting divided into two daughter cells. This is the end of the cell division.


Mitosis – Functions

  • Mitosis helps an organism to grow from a baby to an adult through cell division. 

  • Growth and repair is another function of mitosis.


Mitosis- Its Significance

  • Mitosis develops the zygote into an adult organism.

  • Development and normal growth of an organism are because of mitosis. It also gives a different shape to an organism.

  • Mitosis forms new plant parts like stems, roots etc. and also helps in the repair of any damaged parts.

  • In the case of some crops that are vegetatively propagated, mitosis also helps in asexual propagation.

  • Mitosis leads to the production of daughter cells that are identical and does not allow any recombination or segregation.

  • In animals, mitosis helps to replace the old and worn out tissues and replaces it with new ones.

FAQ (Frequently Asked Questions)

Q1. Do all the cells go Through Growth and Repair?

A1. Some cells like the muscle cells and the nerve cells cannot regrow or get repaired once they form fully. When they are mature it is important to take care of them.

Q2. How does Mitosis help in Repair?

A2. When we get a cut, the cells that are present around the edge of the cut undergo mitosis that helps to repair the cut. The same happens when there is a broken bone.

Q3. Is Cytokinesis a Stage of Mitosis?

A3. No, cytokinesis is not a stage of mitosis but it is a part of the mitotic phase. This results in two daughter cells. Mitosis is related only to the nucleus but cytokinesis divides the cells after the completion of mitosis.

Q4. Is the Mitosis Phase the Same in Plant and Animal Cells?

A4. Yes, the interphase, prophase, metaphase, anaphase and the telophase are the same in plants and animals. However, whereas the animal cells go through cytokinesis, in the plant cells, a new cell plate is created in the middle, and this creates new cells. Once the division is over, the cell plate changes into a cell wall.

Q5. What if There is an Abnormality During Mitosis?

A5. An abnormality in the mitosis stage alters the DNA and this results in many genetic disorders.