2.3.3 The Stages of Mitosis

Stages of Mitosis:

1. Prophase:

• Chromosomes condense, becoming visible as two sister chromatids joined at the centromere.
• The nuclear envelope begins to break down.
• Centrioles move to opposite poles of the cell.
• Spindle fibres start to form from the centrioles.

2. Metaphase:

• Chromosomes align along the equator of the cell (metaphase plate).
• Spindle fibres attach to the centromeres of the chromosomes.

3. Anaphase:

• The spindle fibres contract, separating the sister chromatids at the centromere.
• The chromatids are pulled to opposite poles of the cell, becoming individual chromosomes.

4. Telophase:

• Chromosomes arrive at the poles and begin to decondense.
• A new nuclear envelope forms around each set of chromosomes, creating two nuclei.
• Spindle fibres disintegrate.

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

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

Key Features of Mitosis:

• Maintains the diploid chromosome number in daughter cells.
• Produces genetically identical cells.
• Essential for growth, repair, and asexual reproduction.