Process of Mitosis cell division

Mitosis is derived from the Greek word Mitos meaning twisted thread. The process in which the nucleus and cytoplasm of the original cell divides to form two daughter cells and the chromosome number of the daughter cell is equal to the number of chromosomes of the mother cell is called mitosis. Because the number and quality of chromosomes of the offspring cells created in this process are similar to the mother cells, it is called equational division.

 

Discovery and naming

In 1973, the scientist Strasburger was the first to observe the creation of a nucleus from a nucleus. In 1873 Polish scientist Waclaw Mayzel observed cell division in frog, rabbit and cat corneas and described it in 1875. In 1855, the scientist Rudolf Virchow first explained that new cells are formed by division from previous cells. In 1879, scientist Snyder gave a complete description of the process of mitosis. Mitosis was named by scientist Walter Fleming in 1882. In 1960 Cockraum & Mac-Caulay explained the chemical nature of mitosis cell division. Scientist Walter Whitman called the division of cytoplasm as cytokinesis.

 

Mitosis is a characteristic of cell division

1. Mitosis Cell division occurs in body cells of organisms.
2. It occurs in haploid, diploid and polyploid cells.
3. In this process, two daughter cells are formed from each mother cell.
4. In this process the nucleus and chromosomes of the cell divide once.
5. The chromosome number of the resulting daughter cell is equal to the chromosome number of the mother cell.
6. Wound healing and necessary cell regeneration is done through mitosis cell division.
7. Mitosis cell division occurs in all unicellular and multicellular organisms.
8. In this process the division of the nucleus first and then the cytoplasm takes place.
9. The development and growth of various organs of the organism takes place in the process of mitosis.
10. Mitosis occurs in the formation and growth of the genitalia.
11. Mitosis occurs due to cytokines, steroids, lymphokines, EGF, PDGF etc.
12. The number of cells increases in the process of mitosis.
13. Mitosis causes the cell to increase in size.

Where does mitosis occur?

1. All embryonic cells divide into multicellular organisms by the process of mitosis.
2. The development and growth of various organs of the organism takes place in the process of mitosis.
3. All organelles in multicellular organisms divide by mitosis.
4. Mitosis takes place in the stem tip, root tip, embryonic root, flower bud, primary bud, developing leaf, cambium etc. region of the growing plant.
5. Mitosis occurs in the formation and growth of the genitalia.

 

Mitosis causes cell division

1. Mitosis cell division takes place to fill the wound in any part of the body.
2. Mitosis cell division occurs when the cell has more cytoplasm than nucleus.
3. Mitosis cell division occurs when the amount of DNA in the cell is high.
4. Mitosis accelerates cell division as protein synthesis occurs in the cell.
5. Mitosis Cell division occurs when there is more RNA than DNA in the cell.
6. Cell division is induced by cytokinins, steroids, lymphokines, EGF, PDGF etc.
7. Mitosis Cell division occurs to increase the number of cells.
8. Mitosis Cell division occurs to increase cell size.
9. Different types of metabolism take place in cells. Cell division is necessary for carrying out metabolism.
10. Nucleo-cytoplasmic ratio is maintained through cell division.

 

Why Mitosis is called Equivalent Division

Mitosis occurs in the body cells of organisms. Somatic cells have a diploid number of chromosomes. In this process two cells are formed from one cell. Both the cell nucleus and the chromosomes divide once in the process of mitosis. The resulting daughter cells resemble the mother cells. The chromosome number of the daughter cell is equal to the chromosome number of the mother cell. Hence, mitosis is called symmetrical division.

 

Process of mitosis cell division

Mitosis Cell division is completed in two stages. Karyokinesis and cytokinesis

 

Karyokinesis

The process by which the cell nucleus or karyon divides is called karyokinesis. Mitosis cell division refers to karyokinesis. In 1879, Strasburger and Schleicher discovered the division of the nucleus and named it karyokinesis. Karyokinesis is divided into five stages. These are-

 

 

1. Prophage: The word Prophage is formed from the Greek words pro meaning origin and phage meaning condition.

Prophase is the first and longest phase of mitosis cell division. At this stage, the nucleus of the cell begins to increase in size. Dehydration of water between the chromosomes begins. Chromosomes increase in dye capacity. Chromosomes gradually shrink as CDK compounds phosphorylate proteins. As a result, the chromosomes become progressively shorter, thicker and more visible. At the end of this stage, each chromosome divides longitudinally without the centromere to form two chromatids. In the process of spiralization, the chromatids of the chromosome are stretched like two springs, becoming thicker and shorter. Phosphorylation of proteins causes the nuclear membrane or envelope and nucleolus to disintegrate. At this stage, the creation of the spindle machine begins.

2. Prometaphage: The word Prometaphage is composed of the Greek words pro meaning original, meta meaning middle and phage meaning stage. The stage between prophase and metaphase is called prometaphase.

In the prometaphase stage, the nuclear membrane and nucleolus completely disappear. Chromosomes become more compact, thicker and shorter. The spindle apparatus is formed from centrioles in animal cells and from microtubules in plant cells. Spindles are composed of proteins and are bipolar. The space between the spindle machines is called equator/equator/neutral/intermediate zone. Both poles are called polar regions. Spindle machines are of two types. Spindle fibers and attraction fibers. Spindle apparatuses that extend from one pole to another are called spindle fibers. The spindle apparatuses to which chromosomes are attached are called attraction fibers or chromosomal fibers or traction fibers. Attraction fibers attach to the pea protein at the kinetochore of the centromere. Chromosomes exhibit chromosomal dance by joining filaments. Aster filaments arise from centrioles at the two poles of the spindle apparatus in animal cells.

3. Metaphage: The word Metaphage is formed from the Greek words meta meaning middle and phage meaning state. Mitosis The intermediate stage of cell division is called metaphase.

Metaphase is a short-lived phase. In the process of condensation, the chromosomes become more compact, thicker and shorter. The coiling of chromosomes at this stage is called super coiling. Chromosomes are located at the equator. The arrangement of chromosomes in the equatorial region looks like a plate. It is called equatorial plate or metaphase plate. At the metaphase plate, the smaller chromosomes are arranged on the inside and the larger chromosomes on the outside. The process of arrangement of chromosomes at the equator is called metakinesis. At the end of metaphase, the centromere of each chromosome divides to form two daughter centromeres.

4. Anaphage: The word Anaphage is formed from the Greek words ana meaning motion and phage meaning state. Anaphase is the shortest phase. In this state, the chromosomes move toward each other’s poles, so it is called the motility phase.

During anaphase, the number of chromosomes in cells doubles that of the parent cell. Homozygous chromosomes produced from the same chromosome repel each other. Chromosomes are moved by the contraction of attraction fibers and elongation of the stem body. Chromosomes run at opposite poles. Half of the extraneous chromosomes run towards one pole and the other half towards the other pole. During polar movement, the centromere is the leader and the armature is the follower. Such poleward movement of chromosomes is called chromosomal movement or anaphase movement. In animal cells, the filaments join together to form interzonal fibers or stem bodies. The stem body helps the chromosomes to move towards the poles. Chromosomes are shaped like English letters V, L, J or I at the polar regions. Anaphase or the phase of motion is completed when the missing chromosomes reach the poles.

5. Telophage: The word Telophage is formed from the Greek words telo meaning end and phage meaning state. Telophase is the last stage of mitosis cell division. It is also called interphase.

Telophase is the opposite of prophase. Chromosomes are fixed at opposite poles. Water hydration begins between the chromosomes. As a result, the color or dye capacity of chromosomes decreases. In the process of de-condensation, the coils or patches of chromosomes open up, become narrower and longer and form the nucleoli. The structure of the spindle apparatus breaks down and gradually disappears. Nuclear membrane and nucleolus reappear. Each daughter nucleus has the same number of chromosomes as the mother nucleus. At the end of the telophase phase, cell plates in plant cells and cell membranes in animal cells are furrowed along the equator.