cell cycle Flashcards
What are the three main checkpoints in the cell cycle?
G1 new set of chromosomes. Comes a bit earlier. Cell decides it was to proceed with cell division
G2- copying (DNA and protein). Make sure no damage DNA
M checkpoint: checks is sister chrmatidd attached to micro tubules
G0 – Why would a cell want to enter G0?- all cells stay in G0 permanently?
Cells not planning to go through division. Neural cells, muscles cells (one differenciated, they stay as that cell) , no, they can move out of that cell
Platelet Derived Growth Factor (PDGF)
With signaling molecule, pulls cell out of G0 and initiates through the cell cycle to start diving.
Without, cells will not divide and stay in G0
Defects in these growth or stop signals
signal pathway recognizes that there are cell next to them, (I filled the gap I can stop diving)
Need to turn off that pathway. If it does not turn off, can lead to cancer
Describe in general how cells regulate the activity of cyclins, and
Then how Cyclins can regulate the Cell Cycle
After Cyclins have done their job, what happens to them?
Proteins concentration correlates with cell cycle
Can be degraded by ubiquitin to turn off signal and Can be reused
Cyclin CDK complex forms a dimer
Activated through a kinase (phosphorylates CDK)
it activates the Cdk as a kinase, but it also directs the Cdk to a specific set of target proteins, ones appropriate to the cell cycle period controlled by the cyclin
- CyclinB and CdK21 and the G2/M Checkpoint:
○ What are the main things that this checkpoint is looking to ensure?
G2 checkpoint, cell need to ensure chromosomes are ready, cycline B CDk complex confrims that
How does the regulation of the cyclin itself prevent unwanted advancement
Phos. 3 times.
1. Cyclin B CDK phos to get into nucleus..
2. DePhos to actually become active
a. Enzymes remove a phos to activate CDK
b. Degradation of cyclin B
3. Dephos again to free up CDK
- M Checkpoint:
What is the main thing that this checkpoint is looking to ensure?
What is the very general method that the cell knows the Chromosomes are ready to be separated?
Make sure chromatids is properly attatched to their microtubules
Kinetochores send out signal saying they are not ready. They are still being in the motion of being attached. When signal stops cell can start to pull apart. (when cell goes quiet, itll divide)
G1/S Checkpoint:
○ Why is this checkpoint (so far from the dramatic conclusion), the most consequential of the checkpoints?
- Point of division. Mitosis has to happen
What is RB and how does it assist CyclinE/CdK2 and Cyclin D/CdK4,6 in regulating the checkpoint?
What protein does it hold onto until the cell is ready to advance?
When RB releases that protein, what does it do?
RB protein on its own holds on transcription factor(E2F), factor cannot turn on specific genes its responsible for ( DNA POLY3) and does not divide.
If its on, CDk complexes will phosphorylates RB protein, goes through a change, and drops the transcription factor and can do its job (gene for POLY 3)
Phopholylates: on, and lets go
Not phosphylated, off and will not let go
What is the normal role of a Tumor Suppressor gene? What is its normal response when asked if a cell is ready to advance in the cycle?
What sort of mechanism does a cell use to convince a Tumor Suppressor Gene Protein to allow advancement?
- Code for proteins that control cell division. Usually encondes to not divide, only when necessary
- If the RB protein is phophylated, it can turn on transcription factor
What happens when there is a mutation in a Tumor Suppressor Gene?
cancer
○ P53 is a very short-lived protein in a cell. Why is that good for regulating the cell cycle?
- Turned off quickly , regulates many genes
○ the chromosomal DNA is in poor shape after replication, what two responses might P53 initiate?
it stops the cell cycle at the G1 checkpoint by triggering the production of Cdk inhibitor (CKI) proteins.
The CKI proteins bind to Cdk-cyclin complexes and block their activity buying time for DNA repair.
p53’s second job is to activate DNA repair enzymes. If DNA damage is not fixable, p53 will play its third and final role: triggering programmed cell death so damaged DNA is not passed on.
able to describe their appearance and the key components of the Chromatid pair.
Two sister chromatids with centromeres on each. Centromeres are joined together. Satellite DNA, the DNA at the centromere. Also holds two chromatids together.
