During mitosis, the parent cell divides to produce two daughter cells, each containing an exact copy of the DNA of the parent cell. Mitosis increases the cell number in this way in growth and tissue repair. Candidates should be able to name and explain the events occurring during each stage of mitosis. They should be able to recognise the stages from drawings and photographs.

We always need more cells (to replace old ones and) for growth and tissue repair.

In mitosis, one cell divides into two new cells: the first cell is the parent cell and those produced are daughter cells. The daughter cells are identical to the parent cell because they have the exact same DNA.

There are four phases in mitosis:

Prophase
DNA that was in chromatin form to condenses into chromosome form: that means it associates with proteins and winds itself into a structure. Each chromosome consists of two chromatids (identicle pairs of DNA) which are joined in the middle by centromeres.
Centrosomes move towards the poles (opposite ends) of the cell and begin to form spindle fibers (micro tubules that act like rope).
The nuclear envelope and nucleolus dissolve.

Metaphase
Chromosomes line up in the middle of the cell.
Spindle fibres which attach to the centromere of chromosomes.

Anaphase
Spindle fibres pull one half of each chromosome in each direction, at the same time the centrosomes are moving further apart towards the poles of the cell.

Telophase
Chromosomes reach poles and turn back into chromatin.
The nuclear envelope and nucleolus reform.

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