Mitosis (Edexcel IGCSE Biology)
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Mitosis
Mitosis is defined as nuclear division giving rise to genetically identical cells
Mitosis is used for:
growth
repair of damaged tissues
replacement of cells
asexual reproduction
Most body cells have two copies of each chromosome
We describe these cells as diploid
When cells divide their chromosomes double beforehand (also known as duplication)
This ensures that when the cell splits in two, each new cell still has two copies of each chromosome (is still diploid)
The process of mitosis
Just before mitosis, each chromosome in the nucleus copies itself exactly (forms X-shaped chromosomes)
Chromosomes then line up along the centre of the cell where cell fibres pull them apart
The cell divides into two; each new cell has a copy of each of the chromosomes
The process of cell division by mitosis
Importance of Mitosis
All cells in the body (excluding gametes) are produced by mitosis of the zygote
Mitosis occurs during:
Growth: mitosis produces new cells
Repair: to replace damaged or dead cells
Asexual reproduction: mitosis produces offspring that are genetically identical to the parent
Mitosis is important for replacing cells e.g, skin cells, and red blood cells, and for allowing growth (production of new cells e.g. when a zygote divides to form an embryo)
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