Biology Chapter 6.4Prayer

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pages 116-118

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.

G2 Checkpoint

• Proteins ensure that the DNA has replicated correctly.

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?