SPM Biology 5 Cell Division (Part 3)

What is Mitosis?

Definition:

Mitosis is the division of nucleus to produce 2 daugther cells, with same number and same kind of chromosomes as parent cell.

MITOSIS occurs in…

Somatic cell (2n) = all body cell EXCEPT gametes

MITOSIS….What for?

To ensure the new cells are genetically identical to parents.
- For unicellular organisms, mitosis = asexual reproduction
- For multicellular organisms, mitosis = To replace dead & damaged cell
                                                       = Growth & development of org. by producing new cell

  

Cell Cycle 

Cell cycle is a series of events that take place in a cell. The events involve the growth, replication and division of a cell. The cell will divide and duplicate of its DNA and finally produce 2 daughter cells.

There are 2 major phases:
1. Interphase (G1, S, G2) and
2. Mitotic phase (M phase)

Cell cycle

Cell Cycle - Interphase

Subphases:
- G1 & G2: Cell grows and differentiates by producing protein & cytoplasmic organelles
- S: Synthesis DNA, forming sister chromatids, joined by centromere

NOTES: During these phases, chromosomes is invisible, thread-like chromosomes= chromatin




 

Cell Cycle – Mitotic Phase (M Phase) 

There are 2 processes occur in mitotic phase:

1. Mitosis
2. Cytokinesis

1. Mitosis
There are 4 phases in mitosis:-

1. Prophase
2. Metaphase
3. Anaphase
4. Telophase

1. Prophase

Prophase

• Nuclear membrane disappears.
• Chromosomes start to develop sister chromatids (Chromosomes condense).
• Spindle apparatus forms and migrates towards the end of the cell.

2. Metaphase

Metaphase

• The chromosomes align on the equatorial plane. This is cause by the tension of the pull from both centrosomes.
• Spindle formation is completed.
• The equatorial plane is equal distance from both ends.

 
3. Anaphase

Anaphase

• The sister chromatids are cleaved (split) and become separate daughter chromosomes (they are separated).
• The spindle fibers pull the daughter chromosomes towards their respective ends.

 
4. Telophase

Telophase

• Corresponding daughter chromosomes attach to opposite ends of the cell.
• A new membrane forms around the respective daughter chromosomes.
• The nucleus appears.

NOTES: Mitosis is now complete but not the cell cycle!


This is just a part of the mitotic phase (M phase). I will continue the next process which is Cytokinesis in SPM Biology 5 Cell Division (Part 4). But wait a moment!! Please read through this post in detail, make sure you are fully understood of the phases and processes occured in Cell Cycle before you further proceed.