CFM 2: Cell Cycle

The flashcards below were created by user Anonymous on FreezingBlue Flashcards.

  1. Most cells are in which phase of the cell cycle?
  2. Difference between G1 phase, G0 phase, and post-mitotic cells?
    • G1: average dividing cells
    • G0: quiescent cells (not dividing, but can be stimulated to enter cell cycle)
    • Post-mitotic: incapable of cell division (e.g. mature neurons)
  3. Where in the cell cycle is the R checkpoint?
    Just before G1/S checkpoint
  4. What is the main purpose of the R point in human cell cycle?
    • Checks growth conditions
    • Before R point, checking for sufficient growth factors
    • After R point, growth factors do not matter; the cell is committed to replicating
  5. What happens if a cell does not receive enough growth factors before the R point?
    Stays in G0 phase
  6. CDKs are (active/inactive) on their own
  7. CDKs are activated by ______
  8. 2 different ways p53 acts as a tumor suppressor and protects us from cancer?
    • Induces apoptosis
    • Stops cell cycle by inducing transcription of p21, which is a Cdk inhibitor protein
  9. p21
    Cdk inhibitor protein; transcription induced by p53
  10. p53/p21 pathway in stopping cell cycle
    • DNA damage to UV rays
    • ATM/ATR repair pathway activated
    • Ultimately activating p53
    • p53 induces p21 transcription
    • p21 inhibits G1/S-Cdk and S-Cdk
  11. Wee1
    Phosphorylates CDK1 to inhibit CDK1 activity during S phase
  12. Cdc25
    Phosphatase that dephosphorylates Cdk1 to allow progression from G2 to M
  13. G1 (R point) cyclin and Cdk
    • Cyclin D
    • Cdk4, Cdk6
  14. G1/S cyclin and Cdk
    • Cyclin E
    • Cdk2
  15. S cyclin and Cdk
    • Cyclin A
    • Cdk2, Cdk1**
  16. G2/M cyclin and Cdk
    • Cyclin B
    • Cdk1
  17. Wnt pathway
    Wnt inhibits APC inhibits B-catenin stimulates cyclin D transcription
  18. Rb and its effects on cell cycle
    • Rb binds and inhibits E2F, a transcription factor that stimulates transcription of Cyclin E
    • E2F is activated when Cyclin D-Cdk4 phosphorylates Rb, releasing E2F
  19. How does Cyclin D activation lead to Cyclin E activation?
    • Cyclin D phosphorylates Rb, releasing E2F (to which unphosphorylated Rb is bound and inhibiting)
    • E2F promotes transcription of Cyclin E
  20. How do cyclins/CDKs ensure just one round of DNA replication per cell cycle? Which cyclin/CDK complex does this?
    Cyclin E/Cdk2 phosphorylates pre-replicative complexes on DNA when cells enter S phase, degrading them
  21. Two major ubiquitin ligase complexes in cell cycle control
    • APC (anaphase promoting complex)
    • SCF complex
  22. SCF complex
    • Kind of ubiquitin ligase
    • Has F-box, which is interchangeable and specific to target proteins
    • F-boxes mostly interact with phosphorylated proteins to degrade them; many of the targets are phosphorylated by cyclin/CDKs, which allows substrates to be degraded during specific phases of the cell cycle
  23. 2 functions of Anaphase Promoting Complex (APC)
    • 1. ubiquitin ligase that ubiquitinates Cyclin B (G2/M cyclin)
    • 2. Allow chromosome segregation by ubiquitinating securin (which inhibits separase), activating separase, which unglues cohesin complexes allowing chromosomes to separate
Card Set
CFM 2: Cell Cycle
Show Answers