Cell cycle

  1. G0 phase can be an alternative to
    Self-destruction by apoptosis
  2. Anchorage-dependent cells are those
    That will grow and proliferate normally as long as they are properly attached to the extracellular matrix.
  3. Contact inhibition is when
    Cells will stop growing and proliferating when they come in contact with each other, signaling that the space if filled.
  4. Cancer cells differ in regulation of their growth in that
    They can proliferate in a mitogen, anchorage, and contact inhibition-independent manner and are referred to as being immortal.
  5. A mitogen is a
    chemical substance that encourages a cell to commence cell division, triggering mitosis
  6. Cells in the G0 stage are activated by growth factors that
    turn on cyclin D which binds to cyclin dependent kinases (Cdks) to activate them.
  7. Two key classes of regulatory molecules determine a cell’s progress through the cell cycle.
    • Cyclins
    • Cyclin-dependent kinases
  8. What is the difference between cyclins and cyclin-dependent kinases
    • Cyclins
    • – synthesized at specific stages of the cell cycle
    • – regulatory subunits
    • – no catalytic activity

    • Cyclin-dependent kinases (CDKs)
    • – are constantly expressed
    • – catalytic subunits
    • – inactive in the absence of a partner cyclin
    • – phosphorylates proteins to activate or inactivate them
  9. What determines the downstream proteins targeted in the cell cycle
    Different cyclin-CDK combinationsImage Upload 2
  10. The cyclin that binds to Cdk2 and is the primary molecule responsible for the progression of S phase is
    Cyclin A
  11. G1 phase occurs
    From the end of the previous M phase until the beginning of DNA synthesis

    DNA is 2n - two sets of chromosomes present
  12. What happens in the G1 phase
    • Great amount of protein synthesis
    • –Enzymes required in S phase
    • Mainly those needed for DNA replication
    • –Structural proteins
    • New organelles are being synthesized
  13. During the G1 phase, safeguards exist as proteins known as
    Cyclin-dependent kinases (CDKs)
  14. The G1 CDK proteins activate
    transcription factors for a variety of genes
  15. Phosphorylation of what by a cyclin/Cdk is essential to get beyond the G1 restriction point
  16. Rb and Rb-p represent the unphosphorylated and the phosphorylated forms of the
    retinoblastoma protein
  17. In G0 and early G1, Rb physically associates with what and blocks their transactivation domain.
    E2F factorsImage Upload 4
  18. In late G1, Rb-p releases E2F, allowing
    the expression of genes that encode products necessary for S-phase progression.Image Upload 6
  19. What is true about the relationship between Rb and E2F?
    Phosphorylated Rb cannot bind to E2F
  20. What phase in mitosis has a check point
  21. Cyclin-CDK complexes are
    heterodimeric protein complexes that regulate cell cycle progression
  22. The activity of the cyclin-CDK complexes is tightly regulated because
    They are responsible for cell cycle progression and inducing cellular growth and proliferation
  23. The cyclins are targeted for degradation by
    The ubiquitin-proteasome system
  24. G2 phase is from
    End of S phase until the cell enters mitosis
  25. CDK controls
    Entry into mitosis
  26. Significant biosynthesis occurs during this phase mainly
    Production of microtubules
  27. Inhibition of protein synthesis during G2 phase
    prevents the cell from undergoing mitosis.
  28. MPF promotes the entrance into mitosis from the G2 phase by
    phosphorylating multiple proteins needed during mitosis.
  29. Mitosis promoting factor (MPF)
    Stimulates the mitotic and meiotic cell cycles.
  30. Mitosis promoting factor (MPF) is activated by
  31. If DNA is damaged, the cell cycle is arrested via inactivation of
    Cdc25 phosphatase
  32. What is the function of Cdc25
    It is a phosphatase that activates MPF and CDK
  33. MPF activity is related to the concentration of
    cyclins (esp. cyclin A and B)
  34. What is the function of Wee1
    It phosphorylates cyclin B/Cdk1 to keep it inactive. And inhibits CDK
  35. Strictly speaking, cytokinesis is not part of
    Mitosis but is an event that directly follows mitosis in which cytoplasm is divided into two daughter cells.
  36. Cytokinesis is process that
    Divides the nuclei, cytoplasm, organelles and cell membrane into two cells
  37. Kinetochores are attached
    to spindle fibers which are attached to centrosomesImage Upload 8
  38. Securin is a protein involved in
    control of the metaphase-anaphase transition and anaphase onset (Securin inhibits separase)
  39. Separase is a cysteine protease responsible for
    triggering anaphase from metaphase
  40. Cohesin is the protein complex responsible for
    binding the sister chromatids during S phase, through G2 phase, and into M phase.
  41. The lack of cyclin B allows
    The anaphase promoting complex (APC) to form, which breakdowns securin
  42. The cell cycle can be divided into 2 phases
    an I (interphase) and a M (mitotic) phase.
  43. During interphase the cell
    grows, replicates its DNA and prepares for cell division
  44. Interphase can be divided into what three phases
    G0 (a resting phase), G1 (a cell growth phase, S (a DNA synthesis phase) and G2 (prep for mitosis)
  45. The CDKs are inactive unless
    bound to a cyclin
  46. When they are bound to a cyclin, the CDKs
    phosphorylate other proteins to drive the cell forward through the cell cycle.
  47. What three stages have a check point
    G1 G0 M
Card Set
Cell cycle
Cell cycle