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Cell Cycle 2: Cell Cycle Control

Image Credits: Biology (Campbell) 9th edition, copyright Pearson 2011, & The Internet. Provided under the terms of a Creative Commons Attribution-NonCommercial-ShareAlike 3.0 Unported License. Derived from content by David Knuffke.

Thomas Hattori

on 23 October 2015

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Transcript of Cell Cycle 2: Cell Cycle Control

Cell Cycle Control
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
Internal Controls:
External Controls:
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)
PDGF: Platelet Derived Growth Factor
What are platelets? Why do they make a growth factor?
Positional Inhibition
Normal animal cells must be anchored and not too crowded ("density-dependent").
Cancerous cells don't care
Uncontrolled Cell Division
Mutations Happen!
Every second of every day, your DNA is beset by entropic forces.
You have a whole series of genes that make sure mutated cells don't divide.
...but what happens when these genes get mutated?
"Who watches the watchmen?"
- Juvenal
stimulate cell division
Oncogenes: mutated versions. Always "on".
Tumor Suppressor Genes
inhibits cell division
mutated versions turns it "off".
The Stages of Cancer
Metastasis is what kills people.

How do we treat cancer?
Gleevac: A novel cancer treatment
It's too late to apoptize
DNA Repair Genes
Corrects errors during replication
Mutation allows errors to accumulate
Full transcript