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AP Bio- Information 6: Cell Cycle Control
Transcript of AP Bio- Information 6: Cell Cycle Control
Make Sure You Can:
Describe how cells determine whether or not to divide.
Explain the mechanics of the cell cycle control mechanisms described in this presentation
Explain how cancer develops.
Compare the roll that proto-oncogenes and tumor suppressor genes play in controlling the cell cycle.
Explain how cancer treatments work (and why they are not great for the body).
How is cell division controlled?
Why do people get cancer?
Cells should only divide when they need to.
The cell cycle is under both internal and external control
It's best to think of cell cycle as consisting of a series of "checkpoints" that the cell must pass through in order to be able to divide.
What happens if cells don't pass a checkpoint?
The G1 checkpoint:
A breast cancer cell: It's become a "selfish" cell
Protein molecules that are present in varying concentrations during the cell cycle
Proteins and other environmental signals generated by other cells
Evidence suggesting that there are molecules present during the cell cycle that cause cells to progress
Determines if a cell should replicate its DNA.
From here cells either enter S phase or G0
"Senescence": Cells that have stopped dividing
MPF: Mitosis Promotion Factor
Cdk: "Cyclin-dependent" kinase
Present in a constant amount
Cyclin: the Cdk "on switch"
made in an increasing amount as the cell moves through interphase
MPF: Cyclin + Cdk
turns on other proteins needed for mitosis (e.g. microtuble formation)
No Cyclin = No Mitosis
What kind of feedback is this?
PDGF: Platelet Derived Growth Factor
What are platelets? Why do they make a growth factor?
Normal animal cells must be anchored and not too crowded ("density-dependent").
Cancerous cells don't care
Uncontrolled Cell Division
Every second of every day, your DNA is beset by entropic forces.
You have a whole series of genes that make sure mutated cells dont divide.
...but what happens when these genes get mutaed?
"Who watches the watchmen?"
stimulate cell division
Oncogenes: mutated versions. Always "on".
Tumor Suppresor Genes
inhibit cell division
"The brake pedal"
mutated versions always "off".
Cancer requires mutations in different genes to occur (it's a "multi-step" pathway)
The Stages of Cancer
* The "Knudson hypothesis" Suggested by Carl Nordling, based on the fact that cancer occurs on average as a sixth function of an indivdual's age. Who says math is useless?
A multi-step model of colon cancer development
Metastasis is what kills people.
How do we treat cancer?
Gleevac: A novel cancer treatment
It's too late to apoptize