Topic 7 Flashcards
(18 cards)
List and describe the phases of the eukaryotic cell cycle
G0: Non dividing state
G1: Beginning of cycle-ends with restriction checkpoint. This is the point of no return
S:Synethsis (DNA replication)
G2:More growth happens-preparing for M phase
M phase: Chromosomes divide and new cells form
What happens in Mitosis Prophase?
In prophase, chromosomes condense and nuclei breaks apart. Spindles begin to form
What happens in Mitosis Metaphase?
Chromosomes line up in the middle.
What happens in Mitosis Anaphase?
Chromsomes begin to be pulled apart.
What happens in Mitosis Telophase?
New nuclei forms and membrane begins to pinch.
What happens in Mitosis Cytokinesis?
Two new cells are formed.
Describe CDK
CDK is the main cell cycle control tool. It requires cyclin.
How can CDK be controlled?
CDK can be controlled by binding to cyclin, phosphorlyation/dephosphorylation, by CDK inhibitors and by levels of CDK transcription and translation.
What are some other regulators and what do they do?
There is Wee1, which adds an inhibiting phosphate to CDK
There is Cdc25 which removes the inhibitory phosphate and activates CDK
There is CAK which phosphorylates and activates CDK
Describe cyclins.
Cyclins must be bound to CDK for cell cycle regulation. Cyclin levels change throughout the cycle, according to when they are needed. When they are no longer needed, they are ubiquinated and destroyed.
Describe the G1 checkpoint and the steps.
This checkpoint makes sure cells are ready to enter cell cycle.
1)Cyclin binds CDK
2)Cyclin-CDK phosphorylates RB
3)RB releases E2F
4)E2F enters nucleus and cell moves into S phase
Describe the spindle assembly checkpoint and it steps.
This checkpoint makes sure that the chromatids are connected to the spindle before they seperate
1)Securin secures seperase inactive
2Seperase seperates cohesins holding together chromatids
3)APC ubiquinates securin to release seperase
What is p53?
p53 is a tumor supressor. It is activated during DNA damage and it actviates p21(A CDK INHIBITOR). CDK inhibitors like these pause the cell cycle to allow for DNA repair. If there is no repairing, cell death occurs. (apoptosis).
What is cancer? What are its 2 genes?
Cancer is when cells uncontrollably divide. They have proto onco genes and tumor supressor genes.
Describe proto-onco genes.
Proto-onco genes continue the cell cycle. These can cause cancer.
Describe Tumor-supressor genes.
Tumor supressor genes stop the cell cycle and stop cancers.
Is GOF mutations over active or under active? LOF mutations?
GOF mutations are overactive
LOF mutations are underactive
What are some examples of proto-onco genes and tumor supressors?
Proto-onco: E2F, seperase, CDK
Tumor supressors: P53
