"Checkpoints" are present that will either allow the cell to continue the cycle or stop it ther to repair/assess or kill the cell if repair is impossible.
A. G1 Checkpoint- is DNA replication able to proceed? If so, proteins will tell the cell to continue.
B. G2 Checkpoint- Has the DNA been replicated correctly? Are there enough organelles, skeletal structures, etc. to allow Mitotic Division? If yes, it will proceed to M phase.
C. M Checkpoint- Has mitosis been completed correctly? If no, the cell will die. If yes, it will continue to the C-phase.
III. The G1 Checkpoint and Cancer- There are 2 sets of genes that, if mutated, can cause the Cell Cycle to go out of control and potentially cause cancer.
A. Tumor-Suppressor Genes- produce proteins that will delay the cell cycle at the G1 Checkpoint until the cell is ready to proceed.When one of these genes mutates, a protein will be produced that does NOT stop the cell at the G1 Checkpoint and the cell will grow and divide without being assessed. Problem with that is uncontrolled cell division of useless cells=CANCER.
- Cancer is unrestrained cell growth and division
- The result is a cluster of cells termed a tumor
- Benign tumors
- Encapsulated and noninvasive
- Malignant tumors
- Not encapsulated and invasive
- Can undergo metastasis
- Leave the tumor and spread throughout the body
The p53 Gene triggers the production of DNA Repair enzymes and then allows the cell to pass the G1 Checkpoint if the repair is successful. But if DNA is beyond repair, p53 triggers enzymes that destroy the cell.
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