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28 Cards in this Set

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What role does actin play in cytokinesis?
Actin forms a contractile ring, and through its interactions with myosin II, pinches the 2 cells apart at the cleavage furrow.
G1 DNA-damage checkpoint
If high levels of damaged DNA occur, p53 is expressed, and the cell is stopped.
G1 phase restriction checkpoint
Physiological properties of the cell are checked: cell size, nutrients, matrix attachment. This is the point of no return, once passed, the cell replicates DNA.
What proteins mediate the G1 restriction checkpoint?
E2F family: transcription factors that express important proteins like cyclins and cdks

Rb: Retinoblastoma susceptibility protein. Binds and inhibits E2F. Loss of Rb results in malignancy.
S DNA damage checkpoint
Quality monitor for DNA
What are the checkpoints that occur during G2?
1. G2 DNA damage checkpoint
2. Unreplicated DNA checkpoint: prevents progression to Mitosis until replication complete
When does the spindle assembly checkpoint occur?
During metaphase. Attachment of spindle fibers to kinetochores is checked and cytokinesis blocked if not correct. Triggers apoptosis with irreparable damage.
What causes mitotic catastrophe?
Malfunction at any of the 3 DNA damage checkpoints, or at the spindle assembly checkpt. Results in aneuploidy.
What may lead to cells losing contact inhibition?
Failure to arrest at a restriction checkpoint.
What proteins are instrumental in regulation of cyclins and cdks?
Ubiquitin binds to protein, targeting it for degradation by a proteosome.

CDK inhibitors bind to the complex and inhibit its activity (i.e. p21 and p27)
Describe what happens in apoptosis.
Biological changes followed by morphological changes. Cell shrinks, fragmentation and pyknosis of DNA (irreversible condensing), and membrane blebbing (release of cell contents in membrane enclosed bodies).
The cellular contents are released into the extracellular space during apoptosis (T/F).
False. They are released in apoptotic bodies.
An inflammatory response is not initiated during apoptosis.
True, normally.Apoptotic cells are phagocytosed.
Apoptosis generally involves areas of cells.
False. Usually involved single cells are small areas of cells.
What are some of the biochemical features of apoptosis?
Depolarization of mitochondrial membrane: cyt c is released into the cytoplasm, activating caspases.

DNA break

PS translocation
What happens in the extrinsic pathway of apoptosis initiation?
Ligand for death receptor produced by another cell. Activation of the death receptor (transmembrane) can stimulate binding to a death domain of a docking protein. Caspase cascade initiation occurs.
What is FLIP?
FLIP is a pro-caspase 8 inhibitor protein. It is produced by viruses and some normal cells to prevent apoptosis.
What are the Bcl-2 family pro-apoptotic proteins active in the intrinsic apoptotic pathway.
Bax
Bak
Bad
Bik
Bim
What are the Bcl-2 family anti-apoptotic proteins in the intrinsic apoptotic pathway?
Bcl-2
Bcl-XL
A1
Describe the role of the Bcl-2 family proteins in apoptosis.
Bcl-2 anti-apoptotic proteins are upregulated by growth factors in cells, promoting survival. When they decrease in concentration or are absent, homodimers of the pro-apoptotic proteins initiate apoptosis.
What occurs in the intrinsic apoptotic pathway after initiation of apoptosis?
Due to ROS, cyt c is released into the cytoplasm. It binds to Apaf-1 which activates procaspase 9.

Bcl-2 and Bcl-XL inhibit Apaf-1
How does p53 stimulate apoptosis?
Increases production of Bax and FasR (both pro-apoptotic prots)
Are the intrinsic and extrinsic apoptotic pathways mutually exclusive?
No, interactions exist between the pathways.
Which amino acid in the active site of caspases lends the protein family its name?
Cysteine!
What are the 2 groups of caspases?
Initiators
Activators: cleave targets of apoptosis
What is the default mode for a cell?
Apoptosis! Anti-apoptotic signals must persist for a cell to survive.
What assays can used to detect the presence of apoptosis?
DNA laddering
Annexin V
PARP detection
TUNEL method
What is the role of p53 in apoptosis?
Freaking everything. Binds to damaged DNA and recruits repair proteins to the site. Arrests cell cycle until DNA repaired, and if not, upregulates transcription of Bak and Bax. Also down regulates anti-apoptotic prots.