Mitosis Cell Division - Process and Significant | Biology

Notes | Zoology
Complete Notes on Mitosis Cell Division
For: Science Class 1
Subject: Biology

Mitosis cell division

The process of cell division in which al the chromosomes replicate and separate into two groups having equal number of chromosomes as their parent cell. Thus two nuclei are formed. During the process

Interphase

The nucleus is metabolically active. This phase is divided into 3 sub phases

G1 phase: Protein and RNA synthesis occurs, nucleus appears to contain fine delicate threads, and chromosomes are fully extended.

S phase: DNA and protein synthesis occurs, chromosomes replicate, synthesis of RNA stops.

G2phase: Synthesis of DNA stops, Enzymes are formed, cell organelles multiply.

Karyokinesis

Prophase 

1. Chromosomes become slender elongated distinct and separate threads 

2. Chromatids lie parallel to each other and are connected by Centro mere 

3. Chromosomes become shorter and thicker and Matrix sheath appears around chromatids. 

4. Nuclear membrane and nucleolus start to disappear 

5. Centrioles appear and start to move towards pole.

Metaphase 

1. Spindle fibres appear and centromere also produced fine fibers called tractile fibers. 

2. Spindle fibers connect centromere of each chromosome 

3. All the chromosomes arrange at the equatorial plane of the cell. 

4. The centromere of each chromosome divides into two centromeres in longitudinal way 

5. One centromere of each chromosome is connected with spindle fiber of one pole and another Centro mere is connected with spindle fiber of another pole. 

Anaphase

1. A kind of repulsive force is developed between two centromeres of each chromosome 

2. One of the two centromeres having its own chromatids moves towards one pole and another cnetromere move towards another pole. 

3. Two groups of chromosomes are formed at each pole due to contraction of spindle fibers 

Telophase 

1. Spindle fibers disappear 

2. Chromosomes at each pole become elongated long coiled forming chromatin network 

3. Nuclear membrane and nucleolus reappears 

4. Thus, two nuclei are formed at each pole. 

Cytokinesis 

The process of division of cytoplasm is called cytokinesis 

a. Cell plate Method 

1. Number of vacuoles and vesicles fused together at the middle of cell between two nuclei forming a plate like structures. The plate like structures are called phragmoplast 

2. Cell wall components accumulates at the each side of the cell plate 

3. And single cell is divided into two daughter cells 

4. This method takes place in plant cell. 

b. Cleavage Method 

1. No cell plate is formed in this method. 

2. The cytoplasm is constricted directly from the constriction of cell membrane and ultimately the cell is divided into two parts. 

3. This method takes place in animal cell. 

Significance of Mitosis 

1. It keeps the chromosome number constant and genetic stability in daughter cells, so the linear heredity of an organism is maintained. 

2. It helps in growth and development of zygote into adult. 

3. It plays a significant role in wound healing, replacement of old and decaying and dead cells and regeneration of lost parts. 

4. It helps the cell in maintaining proper size 

5. It also helps in asexual reproduction by fragmentation, budding, stem cutting etc. Through the process, equilibrium is maintained in the amount of DNA and RNA

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