Cellular Division

  1. Why do cells divide?
    • Reproduction
    • Growth and development
    • Tissue renewal
    • Maintain surface area:volume ratio
  2. Types of cellular division
    • Asexual
    • Sexual
  3. Types of asexual cellular division
    • Mitosis
    • Binary Fission
  4. Type of sexual reproduction
  5. How much DNA in your cells?
    • 2 m of DNA per cell
    • Approximately 3 billion base pairs
  6. Genome
    The DNA of a cell
  7. What kind of chromosomes do prokaryotes have?
    Single circular chromosomes
  8. What kind of chromosomes do eukaryotes have?
    • Linear chromosomes
    • Cells often contain two copies of each chromosome (homologous chromosomes)
  9. What are the subunits (nucleotide) of DNA are composed of?
    A nitrogenous base (A,T,C,G), sugar, and phosphate group
  10. Chromosomes
    • Long strand of DNA wrapped around proteins (histones)
    • Chromatin make up chromosomes
  11. Parts of a chromosome structure
    • Centromere
    • Telomere
    • Kinetochore
  12. Centromere
    Condensed region of chromosome
  13. Telomere
    • Region of repetitive DNA sequences at end of chromosome
    • -These acts as buffers
    • -Tells the cell to stop dividing
  14. Kinetochore
    Disc-shaped protein that spindle fibers attach to
  15. What do chromosomes do before they divide?
    • They are duplicated
    • They create sister chromatids
    • Helf together at centromere
  16. When are the sister chromatids are pulled apart?
  17. Bacterial Binary Fission
    • A form of asexual reproduction
    • This happens quickly because there's not as much information and it's easy to get them into the two halves of the cell
  18. Eukaryotic Cell Cycle Steps
    • Mitosis
    • Cytokinesis
    • Interphase
  19. Steps in interphase
    • G1
    • S
    • G2
    • Cells spend 90% of their time in interphase
  20. Gap 1 (G1)
    • Cellular contents, excluding the chromosomes are duplicated
    • Growth, protein synthesis, organelle synthesis
    • -normal function
    • -protein synthesis
  21. Synthesis (S)
    • Each of the 46 chromosomes is duplicated by the cell
    • DNA is duplicated
  22. Gap 2 (G2)
    • The cell "double checks" the duplicated chromosomes for error, making any needed repairs
    • Growth, synthesis of microtubules, cell cycle checkpoints
  23. Best description of interphase portion of the cell cycle
    During interphase, a cell is metabolically active
  24. Two joined copies of a replicated chromosome are called
    Sister chromatids
  25. G0
    • Quiescent or "resting" state, cells not preparing to divide but are metabolically active
    • -Majority of cells in the human body are here
    • -Some cells can be called back (i.e. liver cells)
  26. Mitosis
    • Nuclear division
    • Followed by cytokinesis (division of organelles and cytoplasm)
    • Produces 2 identical daughter cells
    • Typically divided into 5 phases
    • This is a continuous process
  27. Vinblastine is a chemotherapeutic drug because it interferes with microtubule formation, its effectiveness must be related to?
    Disruption of mitotic spindle formation
  28. Prophase
    • Chromosomes begin to condense
    • Spindle apparatus (MTOC) begins to form
    • -"machine" responsible for pulling apart the chromatids
    • -composed of microtubules and other proteins
  29. Prometaphase
    • Nuclear envelope disassembles
    • Spindle fibers attach to kinetochores
  30. Metaphase
    • Chromosomes align along the metaphase plate
    • -occurs because of tug-of-way between the two poles
    • -This is important because you want all of the chromosomes in both parts of the cell split
  31. Metaphase plate
    • Is where the chromosomes line up in the center of the cell
    • It's not a physical structure like the equator
  32. What phase is the shape of chromosome an X
  33. Anaphase
    • Sister chromatids are cut apart
    • -Cohesion that hold them together cleaved by enzymes
    • Sister chromosomes can be pulled to opposite poles
    • -Movement achieved through shortening of microtubules
  34. What marks the beginning of anaphase?
    Cohesion that holds the sister chromatids together are cleaved by enzymes
  35. Which does not occur during mitosis?

    E) replication of the DNA
  36. Telophase
    • Reversal of prophase events
    • Nuclear envelopes reform around DNA
    • Chromosomes unfold back into chromatin
  37. Cytokinesis
    • Division of cytoplasm
    • Not a part of mitosis
    • -begins during telophase
  38. What happens in animals during cytokinesis?
    Cleavage furrow pinches off separated nuclei
  39. What happens in plants during cytokinesis?
    • New cell wall is formed
    • Golgi-derived vesicles bring material to middle
    • -Fuse to form cell plate
  40. How is the cell cycle regulated?
    • Tight regulation is crucial for normal growth and development
    • Controlled by a system of signaling molecules which trigger and coordinate the events of the cell cycle
    • Multiple checkpoints make sure the cell is ready to proceed to the next step
    • -M-phase checkpoints
    • -G1 checkpoint
    • -G2 checkpoint
  41. What are the two main regulatory molecules of the cell cycle clock?
    • Cyclins
    • Cyclin-dependent kinases (cdks)
  42. Cyclins
    Is a regulatory protein who's levels fluctuate cyclically
  43. Cyclin-dependent kinases (cdks)
    • Catalyzes phosphorylation (adds a phosphate) of other proteins to start M phase
    • Present at constant concentrations but usually inactive
    • Active by attaching to cyclins
  44. What is a protein synthesized at specific times during the cell cycle that associates with a kinase to form a catalytically active complex?
  45. What step comes before the M phase-promoting factor?
    G2 checkpoint (G2 to M)
  46. M phase-promoting factor (MPF)
    • Promoting mitosis
    • Protein dimmer consisting of cyclin and cdk
  47. Cells get past cell-cycle checkpoints by..
    Cdks bound to cyclins to phosphorylating other proteins
  48. G1 Checkpoint
    • "Restriction point"- most important in mammals
    • If cell receives: 
    • -Green light it continues to S phase
    • -Red light it exits cell cycle, enters G0
  49. What factors does the G1 checkpoint consider?
    • Is the cell big enough
    • Are conditions favorable
    • Is there any DNA damage, etc?
  50. What comes before the anaphase promoting complex (APC)?
    M phase checkpoint (metaphase to anaphase)
  51. Anaphase promoting complex (APC)
    Complex of 11-13 proteins that marks cell cycle proteins for degradation
  52. How does the MPF protein complex turn itself off?
    Activating a process that destroys cyclin components
  53. External factors for cell regulation
    • Growth factors- platelet-derived growth factor (PDGF)
    • Density- dependent inhibition
    • Anchorage dependence
    • -cells won't divide if it's not anchored to anything
  54. What is the genome made up of?
    All the genes on the chromosomes and all of the chromosomes together
  55. When are CDK's activated?
    • When they attach to cyclins which then allows the check point to occur
    • Referred to M phase promoting factor when CDK is bound to cyclins
  56. What does the M phase check for in a cell? What happens if they aren't there?
    • Targets include:
    • -Condensins
    • -Proteins involved in mitotic spindle formation
    • -Lamins (proteins involved in nuclear envelope assembly/breakdown)
    • If these aren't found, the cell cycle will halt
  57. What do cells do if they need to divide again?
    • If the cell needs to divide again, it goes through the checkpoints starting at G1
    • If not, it goes to G0 where it will no longer reproduce
  58. What is within mitosis and happens from metaphase to anaphase?
    Anaphase promoting complex
  59. What happens in the anaphase promoting complex?
    • If the checkpoint detects an error then it degrade the APC stopping anaphase from occurring
    • APC degrades the securin which is what allows the sister chromatids to separate
  60. Homogenous chromosomes
    Same chromosomes (one from mom and dad)
  61. Sister chromatids
    Only form after replication
  62. Difference during Prophase I in meiosis and mitosis
    • Meiosis has tetrads and crossing over where mitosis just has a line of chromosomes
    • The difference is meiosis has tetrads splitting and mitosis has chromosomes splitting
  63. What comes from mitosis?
    • 2 daughter cells
    • Makes identical sister cells
    • Somatic cells (body cells not germ cells)
  64. Same characteristics between meiosis and mitosis
    • 2 n= diploid (46 chromosomes)
    • -both start with this
    • 4 n= polyploid
    • -both replicate
    • Have sister chromatids and homologous chromosomes
  65. Meiosis
    • Makes 4 daughter cells with half chromosomes to make gametes
    • n= 23 pairs of chromosomes
    • Germ cells
Card Set
Cellular Division