Please enable JavaScript.

Coggle requires JavaScript to display documents.

1.5 Cell division, More on mitosis (closed), CellCycle, Shortest phase,…

- - - - Tumours are the result of mutations - damage to the DNA where base sequences of genes have changed
        
        Many things might damage DNA. Includes specific chemicals, high energy UV or X-ray radiation and some viruses
      - Most gene mutations do not cause cancer but a few do. These mutations are oncogenes and can result in uncontrolled cell division (a tumour).
        
        Several mutations must occur in the same cell for it to become a tumour. This is rare; however, there are many cells in the body and the chance increases over a lifetime.
      - Metastasis is when cell from a primary tumour migrate to other parts of the body and create a secondary tumour
      - Primary tumour
        Once a single tumour cell forms, it divides to create two tumour cells then four and so on.
- - - - Different process in plant and animal cells
        
        ANIMAL
        Plasma membrane is pulled inwards around the equator to form a cleavage furrow
        Accomplished by a ring of protein that can contract
        The cell is pinched into two daughter cells
        
        PLANT
        Vesicles move to the equator where they fuse to form tubular structures
        Tubes merge to form two membrane layers across the equator which develop into the plasma membrane
        These connect to the existing membrane dividing the cytoplasm
        Vesicles bring pectins and other substances, depositing them by exocytosis to form the middle lamella (layer) that will link the cell walls
        Two new cell walls are completed as both daughters cells transport and deposit cellulose at the equator with more exocytosis
    - - S (synthesis)
        DNA replicates
      - G2 (gap 2)
        Enzymes that support cell division are produced
      - G1 (gap 1)
        Organelles and cytoplasm components (like centrioles in animals) replicate
- - - - P3. Towards the end the nucleolus disappears and the nuclear membrane breaks down; ER and Golgi diminish
    - - P1. Chromosomes become shorter and fatter, coiling repeatedly (supercoiling)
      - P2. Microtubules grow from MTOC to form spindle-shaped bridges between the cell poles