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MITOSIS (INTERPHASE (G1 PHASE (cell growth (dependent on growth factors…

- - - - G2 PHASE
        
        grows and prepares for mitosis
        
        (ref. G1)
        
        manufactures proteins
        
        duplicates cell organelles
        
        cell stores energy
        
        checks for errors
        
        cells which pass regulation proceed to M phase
        
        damaged or incomplete DNA is not passed onto daughter cells
        
        moves into dormant G0 phase where cell does not duplicate
      - DNA replication occurs
        
        must be accurate and precise
        
        prevents genetic abnormalities that leads to cell death or damage
        
        using each parental strand as a template, 2 complementary daughter DNA molecules are synthesised in the semi-conservative process
        
        damage to DNA is detected and fixed
        
        cell is now diploid
        
        attached to centromere
        
        23 chromosomes, each with 2 identical sister chromatids
      - centrosome duplicated
        
        microtubule organising centre (MTOC)
        
        composed of 2 centrioles
        
        are microtubule-based cylinders
        
        each composed of 9 triplets of microtubules
        
        positioned perpendicular to one another
        
        function
        
        formation of mitotic spindle fibres
        
        spindle fibres are hollow tubes made up of tubulin (protein subunits)
        
        each cell has 1 centrosome but with cell division 2 centrosomes are needed (1 for each daughter cell)
    - - synthesis of cell organelles
        
        mitochondria
        
        involved in protein synthesis
        
        ribosomes
      - build up energy store
        
        requires nutrients
      - undergoes protein synthesis
        
        manufactures proteins
        
        histones
        
        ribosomal proteins
        
        tubulin (spindle fibres - preparation for mitosis)
      - dependent on growth factors
        
        room for growth
        
        sufficient nutrients (like amino acids for protein synthesis)
        
        temperature
    - - somatic cells need more time vs embryo cells have very short G1 phase
    - - DNA in chromatin structure
        
        note: regulation in protein synthesis still occurs (just not on chromosomal level)
- - - - separated chromatids are each individual chromosomes
        
        ensures each daughter cell has an identical set of chromosomes to parent cell
  - - - ANAPHASE
        
        TELOPHASE
        
        chromosomes reach respective poles
        
        form genetic material of daughter nuclei
        
        chromosomes uncoil to form chromatin
        
        spindle fibres disintegrate
        
        nuclear envelope reforms around chromosomes
        
        cell now has a nucleus
        
        nucleolus reappears
        
        LATE TELOPHASE
        
        division of cytoplasm begins
        
        centromere of each chromosome divides
        
        sister chromatids in each chromosome separates
        
        each sister chromatid is now a chromosome
        
        daughter chromosomes move centromere first to opposite poles of spindle
        
        due to shortening of spindle fibres
        
        caused by removal of tubulin
        
        spindle fibres are attached to kinetochore
        
        1 more item...
        
        in a distinct V shape
        
        because sister chromatids are joined at centromere
        
        cell elongates
        
        nonkinetochore microtubules lengthen
      - chromosomes align on metaphase plate (equator)
        
        equator is equidistance between spindle's 2 poles
        
        centromeres lie on equator
      - spindle fibres attach to kinetochores
        
        forms kinetochore microtubules
    - - chromosomes consists of 2 identical sister chromatids joined at centromere
        
        kinetochore (protein) assembles at centromere
    - - nucleolus disappears
      - phosphorylation of proteins on inner surface of nuclear envelope
      - no nucleus (ref. nucleus structure - must have nuclear envelope and nucleolus)
    - - important because spindle fibres attached to centromeres ultimately pull chromosomes towards centromeres - if they are in opposite ends of the cell, when the cytoplasm splits each centromere will be in a different cell
      - centrioles develop short microtubules (aster) that cover centrosomes
      - mitotic spindle fibre (different form of microtubules) extended from centrioles
        
        poles of spindle fibre is ends: one pole is attached to centriole, the other is later attached to chromosome
    - - spindle fibres fully formed
      - chromosomes fully visible (condensed)
      - centrosomes at opposite poles of cell
      - no nuclear envelope or nucleolus
- - - - daughter cells are genetically identical to parent cells
      - same number and type of chromosomes
        
        ensured through
        
        semi-conservative DNA replication
        
        sister chromatids are genetically identical
        
        arrangement of chromosomes in metaphase
        
        ensures that chromosomes are shared equally
        
        proper formation and shortening of spindle fibre important in making sure sister chromatids are pulled to opposite poles (proper separation)
    - - by allowing for growth, replacing dead or damaged cells
        
        during growth of a multicellular organism
        
        repair of worn out parts of the body
        
        basis of asexual reproduction
        
        but prokaryotes undergo binary fission not mitosis because
        
        no nucleus - mitosis is the division of nucleus
        
        no centromeres - spindle fibre's can't attach to chromosomes and pull them apart
- - - - animal cells
        
        cleavage furrow develops in cell membrane
        
        cell membranes in furrows join up
        
        completely separates daughter nuclei
      - plant cells
        
        Golgi vesicles line up in the middle of the parent cell
        
        vesicles fuse
        
        forms cell plate
        
        cell plate extends outwards across equator of parent cell
        
        contents of vesicles (secretory proteins) contributes to cell wall of daughter cell
        
        membrane of vesicles forms membrane of daughter cells
        
        cell plate fuses with parent cell wall and cell membrane
        
        1 more item...
- - - - DNA replication is complete and accurate
      - no DNA damage
      - chromosome to spindle attachment done correctly
    - - G2 CHECKPOINT
        
        METAPHASE CHECKPOINT
        
        checks for
        
        all chromosomes attached correctly to spindle fibres
        
        prepares for anaphase
        
        presence of all chromosomes
        
        appropriate tension between opposite poles
        
        checks for
        
        DNA integrity (undamaged)
        
        DNA replication (accurate and complete)
        
        if criteria not met
        
        cell cycle halted
        
        DNA repairs occur
        
        if damage is irreparable
        
        cell undergos apoptosis (programmed cell death)
        
        2 more items...
      - checks for
        
        size of the cell
        
        large enough to divide
        
        nutrients availibility
        
        to support daughter cells
        
        molecular signals
        
        appropriate growth signal
        
        DNA integrity
        
        undamaged DNA
      - if no growth signal (criteria not met)
        
        exit cell cycle
        
        enter non-dividing dormant G0 phase
        
        most somatic cells in G0 phase