Two nuclei from one - Mitosis - Mindmap in A Level and IB Biology

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Created by: Steff06
Created on: 06-04-16 13:08

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Mitosis
- Organisms need to produce genetically identical daughter cells for GROWTH, REPAIR and REPLACEMENT.
- Mitosis refers to the process of NUCLEAR DIVISION where 2 genetically identical nuclei are formed from one parent cell nucleus.
- 4 stages in mitosis:
  - PROPHASE - Replicated chromosomes SUPERCOIL (shorten and thicken).
  - METAPHASE - Replicated chromosomes line up down the MIDDLE of the cell.
  - ANAPHASE - Replicas of each chromosome are pulled APART from each other towards OPPOSITE poles of the cell.
  - TELOPHASE - 2 new nuclei are FORMED.
- PROPHASE = Chromosomes shorten and thicken and consist of a pair of sister chromatids. The nuclear envelope breaks down and disappears. The centriole divides into 2 and each moves to opposite poles to form the spindle.
- METAPHASE = Chromosomes move to the central region of the spindle and each becomes attached to a spindle by its centromere.
- ANAPHASE = Replicated sister chromatids are separated from each other when the centromere splits. The spindle fibres shorten, pulling the sister chromatids further away from each other towards the poles.
- TELOPHASE = As the sister chromatids reach the poles of the cell, a new nuclear envelope forms around each set. The spindle breaks down and disappears. The chromosomes uncoil and can no longer be seen under a light microscope.
- CYTOKINESIS = The whole cell splits to form 2 new cells, each containing a full set of chromosomes identical to the original parent cell.
- In PLANTS, only MERISTEM cells can divide this way.