biology chapter 5 - pbworkssdoshi.pbworks.com/w/file/fetch/100906819/biology5-4-1.pdf · biology...
TRANSCRIPT
Tumor Suppressors• Tumor suppressors are proteins that inspect newly replicated
DNA and stop tumors from forming.
• For example, if DNA is damaged, the cell does not continue cell division.
BRCA1 gene• Normally, BRCA1 encodes a protein that functions as a tumor
suppressor.
• The mutant version does not do this. Therefore, the mutant version of BRCA1 causes tumors.
Regulation of Cell Cycle
• Each checkpoint determines whether the cell should be allowed to continue through the cell cycle.
• There are 3 check points: one during G1 (G1 checkpoint) one during G2 (G2 checkpoint), and the last during metaphase (metaphase checkpoint).
G1 Checkpoint
• At the G1 checkpoint, proteins decide if the cell has grown enough to make 2 daughter cells.
Metaphase Checkpoint • Proteins at metaphase
confirm that all chromosomes are duplicated and attached to microtubules
Proto-oncogenes and Oncogenes
• Proto-oncogenes are genes that encode proteins which regulate the cell cycle.
• Oncogenes are mutated proto-oncogenes.
• Proto-oncogenes and Oncogenes work together to create healthy cells and prevent damaged cells from being made at the cellular checkpoints.
Cancer • Cancer is more common in the elderly.
• Older people have more cells that go through cell division.
• Older people have more cells exposed to carcinogens.
• This increases risk of cancer.
Questions 6-4
1. What are tumor suppressors?
2. What are the 3 checkpoints?
3. What happens at the G1 checkpoint?
4. What happens at the G2 checkpoint?
5. What happens at the metaphase checkpoint?
6. What are proto-oncogenes?
7. What are oncogenes?
8. What does proto mean?
9. What does onco mean?
10. What do proto-oncogenes and oncogenes do?
11. Who is at more risk for cancer?
12. Why are they at risk for cancer?