Come and Learn Mitosis

Come & Learn Mitosis

Introduction to Mitosis

• Mitosis is a type of cell division. It produces new cells (daughter cells) that are genetically identical to its parent cells.
  


• The division of mitosis in cells usually produces cells known as somatic cells.
  


• Mitosis is important:
  
  
  
  1. To produce new cells for growth.
  2. To replace old cells that are worn out, damage or dead.
  3. For asexual reproduction of unicellular animals, in primitive living things and some plants.


• The production of daughter cells that are genetically identical to its parent cells in mitosis is important to:
  
  
  
  1. Continue with the specific cell functions of their parent cells with a particular tissue.
  2. To avoid the disturbance in the stable internal environmental of life or its processes.
  3. Produce offspring that have the complete functions of an adult organism to ensure the survival of that species.


• Mitosis occurs in the process of cell division. Mitosis and the cytokinesis together form the mitotic phase in the cell cycle that happens at the last phase of the cell cycle after the G1 phase, S phase, and G2 phase known as the interphase. The figure 1.1 below shows the cell cycle consisting of interphase and mitotic phase. Interphase is the preparation of the cell before undergoing the mitotic phase.
  

Process of Mitosis

There are four phases involve…

1. Prophase

• Chromatids condense
• The nucleolus disappears
• Nuclear membrane disappears
• Paired centrioles move to opposite ends of the cell
• Spindle form

2. Metaphase

• Sister chromatids line up at the equator
• Each centromere attaches itself to the spindle fibre
• Centromere divides at the end of the metaphase

3. Anaphase

• Kinetochores begin to contract increasing the separation of sister chromatids. The separated chromatids are called chromosomes
• They are pulled apart towards the opposite poles by the contraction of spindle fibres
• Anaphase is completed when a complete set of chromosome arrive at each pole

4. Telophase

• Sister chrometids reach opposite poles
• A nuclear envelope begins to form around each set of chromosomes to form two nuclei cell
• The spindle fibres disappear and centrioles replicate
• Nuclear membrane re-forms around the chromosomes and the nucleolus reappears in each nucleus
• Chromosomes uncoil, lengthen becoming invisible called chromatin

Cytokinesis

After the mitotic division of nucleus, the division of the cytoplasm occurs, known as cytokinesis. At the end of cytokinesis, the organelles and other contents of the parent cell are equally divided between the two daughter cells. Cytokinesis in animal and plant cells is different.

In an animal cell, the cell membrane at midpoint of the parent cell constricts in to form a cleavage furrow. Constriction continues, and finally the cell membrane on each side joins up, separating the cytoplasm in to form a cleavage furrow.

In a plant cell, vesicles produced by the Golgi body containing carbohydrates gather at the equator of the parent cell. The vesicles fuse together to form a cell plate. Gradually, cellulose builds on each side of the cell plate forming the cell walls of two daughter plant cells.