Mitosis

Mitosis is a process in which a single cell divides into two identical daughter cells (cell division).

Mitosis > one cell divides once to form two identical cells

The major purpose of mitosis is for growth and to replace worn out cells. If not corrected in time, mistakes made during mitosis can result in changes to DNA, that can potentially lead to genetic disorders.

Stages of Mitosis (5)

1. Interphase

• The DNA in the cell is copied in preparation for cell division. This results in two identical full sets of chromosomes
• Outside of the nucleus are two centrosomes, each containing a pair of centrioles. These structures are critical for the purpose of cell division
• During interphase, microtubules extend from these centrosomes

2. Prophase

• The chromosomes condense into x-shaped structures that can be seen under a microscope
• Each chromosome is composed of two sister chromatids containing identical genetic information
• The chromosomes pair up so that both copies of chromosome 1 are together, both copies of chromosome 2,3,4,5… and so on, are together
• At the end of prophase, the membrane around the nucleus dissolves away, releasing the chromosomes
• The mitotic spindle consisting of microtubules and other proteins, extends across the cell between the centrioles as they move to opposite poles of the cell

3. Metaphase

• The chromosomes line up neatly end-to-end along the centre (equator) of the cell
• The centrioles are now at opposite poles of the cell with the mitotic spindles fibers extending from them
• The mitotic spindle fibers attach to each of the sister chromatids

4. Anaphase

• The sister chromatids are then pulled apart by the mitotic spindle, which pulls one chromatid to one pole, and the other chromatid to the opposite pole

5. Telophase

• At each pole of the cell, a full group of chromosomes gather together
• A membrane forms around each group of chromosomes forming a new cell nucleus for each (2)
• The single cell then pinches in the middle to form two new daughter cells, each containing a full set of chromosomes within a nucleus. This is known as the cytokinesis process

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