2.3.2 Mitosis

Key Features of Mitosis:

• Produces two identical daughter cells.
• Each daughter cell has the same number of chromosomes as the parent cell (diploid).
• Ensures genetic consistency, meaning no genetic variation arises from mitosis.

Stages of Mitosis:

1. Prophase:

• Chromosomes condense, becoming visible as two sister chromatids joined at the centromere.
• The nuclear envelope breaks down.
• Spindle fibres begin to form, extending from the centrioles.

2. Metaphase:

• Chromosomes line up along the equator (middle) of the cell.
• Spindle fibres attach to the centromeres of each chromosome.

3. Anaphase:

• The spindle fibres contract, pulling the sister chromatids apart.
• The chromatids are now individual chromosomes and are pulled to opposite poles of the cell.

4. Telophase:

• Chromosomes arrive at the poles and decondense (become less visible).
• The nuclear envelope reforms around each set of chromosomes, forming two nuclei.
• The spindle fibres disintegrate.

5. Cytokinesis (not part of mitosis but follows it):

• The cytoplasm divides, producing two separate daughter cells.
• In animal cells, this involves the cleavage furrow.
• In plant cells, a cell plate forms to separate the cells.

Importance of Mitosis:

1. Growth:

• Increases the number of cells in an organism during development.

2. Repair:

• Replaces damaged or dead cells to maintain tissue health.

3. Asexual Reproduction:

• Produces offspring in some organisms (e.g., amoeba, yeast).

Comparison of Mitosis and Meiosis:

Feature	Mitosis	Meiosis
Purpose	Growth, repair, asexual reproduction.	Production of gametes (sexual reproduction).
Number of divisions	One.	Two.
Number of daughter cells	Two (identical).	Four (genetically unique).
Genetic variation	None (identical cells).	Present (due to crossing over and independent assortment).