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Mitosis (Edexcel IGCSE Biology: Double Science)
Revision Note
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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