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| 6.2 |
Cell Cycle and Mitosis |
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- The division of the nucleus, followed by cytoplasmic division (cytokinesis) that produces two genetically identical daughter nuclei.
- Controlled by the cell cycle; interphase (G1, S, and G2 phase) and M phase.
- After mitosis is completed, cytokinesis occurs to form two identical daughter cells.
- Cytokinesis occurs in animal and plant cells.
- Animal cells form a cleavage furrow to form two separated individual cells.
- Plant cells form a cell plate to produce two separate cells.
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| The Cell Cycle and M phase: |
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Interphase
G1 phase
- Synthesized proteins and new organelles
- The metabolic rate of the cell is high
- Chromosomes are thin, known as chromatin
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S phase
- Synthesized DNA
- Form two identical sister chromatids through DNA replication
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G2 phase
- The cell continues to grow
- Enzymes for cell division are synthesised
- The cell accumulates energy
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M phase
Prophase
- Chromosomes become condense and visible under the microscope
- Two sister chromatids joined at the centromere
- Centrioles move to the opposite poles
- Spindle fibres are formed
- Nucleolus and nuclear membrane disappear
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Metaphase
- Chromosomes aligned on the metaphase plate
- Spindle fibres form completely
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Anaphase
- Spindle fibres pull the two sister chromatids at the centromere
- Causing the two sister chromatids to separate
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Telophase
- Begins when both chromosomes reached completely at the poles
- Chromosomes uncoiled and became chromatin again
- Spindle fibres disappear, and the nuclear membrane begins to form
- Now the M phase is complete
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| The necessity of mitosis: |
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- For embryo development and organism growth, mitosis ensures that rapid cell growth occurs.
- When the body is injured, mitosis will produce new cells to replace cells that are dead or damaged.
- Stem cell therapy uses stem cells from bone marrow to treat damaged cartilage.
- Through the mitosis process, the lizard is able to grow a new tail (regeneration) if the tail breaks.
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| Effects of Uncontrolled Mitosis: |
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- Can produce cancer cells.
- Cancer cells are abnormal cells that compete for nutrients and energy with the normal cells for growth, which cause the normal cells to malfunction and die.
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