11 - Cell Cycle Checkpoints Flashcards
If you were a normal cell dividing, what do you want to check?
DNA at G2 (after S-phase) = to see if DNA pol made a mistake = mismatches »_space;> need repairs
What is one reason explaining why one mutation is never enough to cause a cell to transform into a cancer cell?
cell has a lot of tumor-suppressors
What does Wee1 kinase do?
pauses cell cycle by phosphorylating CDK = changes shape so it doesn’t work
What does Cd25 phosphatase do?
resumes cell cycle by dephosphorylating CDK = change shape = works again
What will happen to a cell due to a Wee1 mutation?
cells will be smaller but more of them | because they did not have enough time to check and grow to right size
What will happen to a cell due to a Cd25 mutation?
cannot reactivate CDK = cells are larger and does not divide | larger = bc had so much time to grow
What are CKIs? What is an example of one?
CDK complex inhibitor | ex: p27 | inactivates CDK-cyclin complex by latching onto it = renders it inactive
What is the status of CDK in non-proliferating cells?
held inactive by CKI »_space;> Rb = active = no free E2F = no cyclins made
What is the status of CDK in proliferating cells?
CKI = inactive »_space;> CDK = active; Rb = active = release E2F = cyclins made »_space;> expression of S-phase genes activated
What is non-disjunction?
chromatids don’t separate because spindles are not working = aneuploidy
What is APC?
protein that tags ubiquitins on securin to activate separase
What is separase?
cleaves the cohesins that hold the chromatids together
What is securin?
sequesters and inactivates separase
What would happen if we went into G1 and all of our M-cyclins are still there?
cell will skip S-phase and divide again
Which cells do not make M-cyclins and why?
germ cells = they don’t undergo S-phase (only meiosis)
