- Cell is actively synthesising proteins
- Chromosomes invisible
- Occupies most of the cell cycle
- Known as the resting phase because no division takes place
- Divided into three parts
- First growth (G1) phase, when the proteins from which cell organelles are synthesised are produced
- Synthesis (S) phase, when DNA is replicated
- Second growth (G2) phase, when organelles grow and divide and energy stores are increased
1 of 9
- Chromosomes become visible
- Nuclear envelope disappears
- Nucleolus disappears
2 of 9
- Chromosomes arrange themselves at the centre of the cell
- Spindle forms
3 of 9
- Each of the two threads of a chromosome (chromatid) migrates to an opposite pole
- Spindle fibres attached to the chromatids contract
4 of 9
- Nuclear envelope reforms
- Chromatids reach poles and become indistinct
- Nucleolus reforms
- Spindle disintegrates
5 of 9
Importance of Mitosis: Growth
- When two haploid cells (e.g. a sperm and an ovum) fuse together to form a diploid cell, this diploid cell has all the genetic information needed to form a new organism.
- If the new organism is to resemble its parents, all the cells that grow from this original cell must possess the same set of genetic information.
- Mitosis ensures that this happens.
- The cell firstly divides to give a group of identical cells.
6 of 9
Importance of Mitosis: Differentiation
- These cells change, or differentiate, to give groups of specialised cells, e.g. epithelium in animals or xylem in plants.
- These different cell types each divide by mitosis to give tissues made up of identical cells which perform a particular function.
- This is essential as the tissue can only function efficiently if all its cells have the same structure and perform the same function.
7 of 9
Importance of Mitosis: Repair
- If cells are damaged or die, it is important that the new cells produced have an identical structure and function to the ones that have been lost.
- If they were not exact copies then the tissue would not function as effectively as before.
- Mitosis is therefore the means by which new cells replace dead or damaged ones.
8 of 9
- Cancer is a group of diseases caused by a growth disorder in cells.
- It is the result of damage to the genes that regulate mitosis and the cell cycle.
- This leads to uncontrolled growth of cells.
- As a consequence, a group of abnormal cells, called a tumour, develops and constantly expands in size.
- Cancers can develop in any organ of the body.
- Drugs used to treat cancer (chemotherapy) disrupt the cell cycle by:
- preventing DNA from replicating, e.g. cisplatin
- inhibiting the metaphase stage of mitosis by interfering with spindle formation, e.g. vinca alkanoids
9 of 9