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Cell division mitosis meiosis
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Cell division mitosis meiosis

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Powerpoint presentation of cell cycle and cell division

Powerpoint presentation of cell cycle and cell division

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  • 1. What Cellular Process Allows
    Single cell
  • 2. Cell Division
  • 3. Cell Division Cycle
    Is essential for
    Mother and daughter cells are identical
    Cell turnover
    Components of the nucleus and cytoplasm divide during cell cycle
    Cytokinesis is the division of the cytoplasm
  • 4. Cell Cycle
    Control of cell division is complex & precise
    Steps occur in sequence
    Must know when to proceed/wait
  • 5. The eukaryotic cell cycle
  • 6. Normal Growth Conditions
    Protein content increases
    RNA synthesis continues, except during cell division (M phase)
    Overall growth is a steady process
  • 7. Interphase
    Decision making time for cell
    Should cell replicate??
    Mitosis?? Can lead to cancer
    Often looks like nothing is happening
    Makes up 90% of the time
    Has 3 subphases
    G1 – separates the end of mitosis from the next round of DNA replication
    S phase – DNA replication
    G2 phase – gap between S phase and Mitosis
    Cells can remain in G1 for weeks or even years
  • 8. G0 Phase
    There are times when a cell will leave the cycle and quit dividing.
    This may be a temporary resting period
    Can be permanent
    ie a cell that has reached an end stage of development and will no longer divide (e.g. neuron).
  • 9. G1 phase
    Cells increase in size
    Produce RNA and synthesize protein.
    An important cell cycle control mechanism activated during this period (G1 Checkpoint) ensures that everything is ready for DNA synthesis.
  • 10. S Phase
    To produce two similar daughter cells
    the complete DNA instructions in the cell must be duplicated.
    DNA replication occurs during this S (synthesis) phase.
  • 11. G2 Phase
    Cells continue to grow and produce new proteins.
    At the end of this gap is another control checkpoint (G2 Checkpoint) to determine if the cell can now proceed to enter M (mitosis) and divide.
  • 12. Practical implications
    • Most cells have limited number of divisions
    • 13. Stem cells
    • 14. Divide indefinitely
    • 15. Can make many types of cells
    • 16. differentiate
    • 17. Mistakes can lead to tumours
  • When Things go Wrong
  • 18. Mitosis
  • 19. Mitosis
    Mitosis = process of nuclear division
    Occurs in somatic cells (not germ-line)
  • 20. Mitosis
    M-Phase is divided into 6 stages
    Based on observations using the light microscope on living cells and a mixture of light and electron microscopy
    Telophase cytokinesis (non-nuclear)
  • 21. Mitosis - Prophase
    Prophase (beginning of mitosis)
    Transition from G2 to M is not clear
    Chromosomes condense (shorted and thicken)
    Nuclear envelope disintegrates
    Chromosomes are composed of 2 identical (sister) chromatids
    Centromeres have divided but remain together
    Spindle fibres begin to grow from the centrosome
  • 22. Mitosis - Metaphase
    Chromosomes move to the equator of the cell (metaphase plate)
    Spindle fibres become attached to the sister chromatids
    Spindle apparatus is complete
  • 23. Mitosis - Anaphase
    Sister chromatids begin to separate and form chromosomes
    Chromatids move towards opposite poles (1 um per minute
    Can be delayed until all chromosomes are on the metaphase plate
  • 24. Mitosis - Telophase
    Sister chromatids arrive at opposite poles
    Reverses the steps of prophase to return to interphase
    Chromosomes uncoil & protein synthesis begins
    Nuclear envelope reforms
    Cytokinesis takes place
    Cell entered G1 phase
  • 25. Cytokinesis
    • Contractile ring forms
    • 26. Start by a groove in the membrane
    • 27. Organelles need to be produced
    • 28. not distributed equally between daughter cells
    • 29. Mitochondria and chloroplasts split between each daughter cell
    • 30. Golgi and ER break up and the daughter cells inherit components
  • 31. Meiosis
    Grant McKenzie
  • 32. What is meiosis?
    Gamete formation
    Sperm/pollen and egg
    From diploid (2 copies) to haploid (1 copy)
    Resorted NOT doubled
    4 daughter cells contain a complete set of chromosomes
    Promotes genetic diversity
  • 33. Genetic Diversity
    Meiosis gives rise to genetic diversity
    Crossing over
    Occurs between homologous chromosomes not sister chromatids
    Chance combination of gametes during fertilisation
    Genetically diverse sperm and eggs can unite
  • 34. Meiosis
    Involves two cell Divisions
    Meiosis I – a reduction from 2n to 1n
    Meiosis II resembles mitosis (1n to 1n)
  • 35. Meiosis – Prohase I
    Similar to prophase of mitosis
    chromosome duplication & spindle formation
    Chromosomes condense and are attached to the nuclear membrane
    Paring of homologous chromosomes
    Homologous chromosomes join along their length
    Chromosomes fuse together and are referred to as bivalents
  • 36. Overview of DNA Synthesis
    In each cycle of cell division, the cell first makes a copy of all of the DNA in each of the chromosomes
  • 37. Meiosis – Prohase I
    Crossingover occurs throughout prophase I
  • 38. Crossing Over
    Homologous chromosomes
    Recombinant chromatids
    Adjecent homologous chromosomes break and swap genetic material
    Greatly increases the genetic variation
    Tetrads form chiasmata, X shapped configuration that marks crossing over
  • 39. Meiosis - Metaphase I
    Nuclear membrane breakdown
    Development and attachment of the machinery to pull the tetrads (chromosomes) apart (kinetochore & microtubules)
    Tetrads move to the equatorial plate
    There is no splitting of the sister chromatids like mitosis
  • 40. Meiosis – Anaphase I
    Cohesin breaks down between the centromeres
    homologous chromosomes are pulled apart
    Called a reductional division
    For every tetrad there is now 1 chromosome in the form of a chromatid pair called a dyad
    Located at each pole
    Each daughter cell is haploid
  • 41. Meiosis - Telophase I & Prophase II
    Telophase I does not occur in all species
    Chromosomes enter an interphase configuration as cytokinesis takes place
    No chromosome duplication occurs
    Nuclear envelope reforms
    Cell enters Prophase II
  • 42. Meiosis II – Prophase II
    Meiosis II is basically a mitotic division
    Chromatids from each chromosome are pulled apart to opposite poles
    For each original cell entering Meiosis I, 4 haploid cells emerge at telophase II
    Meiosis II is an equational division
    Reduces the amount of genetic material per cell by half, does not reduce the chromosome number by 2
  • 43. Cell Division - Cytokinesis
    Contractile ring forms
    Does not always occur after mitosis
    Start by a furrowing of the membrane
    Organelles need to be produced
    need not be distributed equally between daughter cells
  • 44. Meiosis square Dance
  • 45. Meiosis vs Mitosis