Question

1. in which of the following circumstances would a cell undergo apoptosis? a dna damage in a cell cannot be repaired at a cellular checkpoint. b a cell becomes cancerous. c a cell successfully completes the g₁ phase of the cell cycle. d a cell successfully completes the m phase of the cell cycle. 4. the p53 gene in mammalian cells is known to stop the cell cycle in response to damaged dna. if this gene is damaged without repair, which of the following is most likely to occur? a the cell will immediately undergo apoptosis. b the cell cycle will be disrupted in the defective cell. c growth factors will allow the cell to divide normally. d damaged dna will remain unrepaired and a tumor may form. 5. patients with type - 2 diabetes can develop wounds, often on their feet, that do not heal properly. platelet derived growth factor (pdgf) is a promising topical treatment for these wounds. which of the following best explains how pdgf may help in treating diabetic wounds? a pdgf signals apoptosis in the cells surrounding the wound. b pdgf increases insulin receptivity to decrease blood sugar in diabetic patients. c pdgf regulates the cell cycle via internal checkpoints to ensure proper cell division. d pdgf binds to the surface of cells to promote tissue growth to close the wound. which of the following best describes the purpose of chemotherapy drugs used in the fight against cancer? a chemotherapy drugs allow cells to live a normal life span by preventing the cells from dying prematurely. b chemotherapy drugs work to normalize the cell cycle by changing the cells genetic code. c chemotherapy drugs work to disrupt the cell cycle of rapidly dividing cancer cells. d chemotherapy drugs are used to boost the immune system and increase the white blood cell count.

Explanation:

1. Question 3: Apoptosis is programmed - cell death. When DNA damage cannot be repaired at a cellular checkpoint, the cell undergoes apoptosis to prevent the propagation of damaged genetic material. Other options are incorrect as cancerous cells avoid apoptosis, and normal cell - cycle completion does not trigger apoptosis.
2. Question 4: The p53 gene is a tumor - suppressor gene. If it is damaged without repair, the cell's ability to stop the cell cycle in response to damaged DNA is lost. So, damaged DNA will remain unrepaired, and a tumor may form. The cell will not immediately undergo apoptosis as the apoptosis - triggering mechanism related to p53 is compromised. The cell cycle will not be properly regulated, and growth factors cannot override the damaged p53 - related control.
3. Question 5: Platelet - derived growth factor (PDGF) is a growth factor. Growth factors promote cell growth and division. In the context of wound healing, PDGF binds to the surface of cells to promote tissue growth to close the wound. It does not signal apoptosis, increase insulin receptivity for blood - sugar control, or mainly regulate the cell cycle via internal checkpoints for wound - healing purposes.
4. Question 6: Chemotherapy drugs target cancer cells. Cancer cells divide rapidly. Chemotherapy drugs work to disrupt the cell cycle of these rapidly dividing cancer cells, leading to cell death. They do not allow cells to live a normal life - span, nor do they primarily boost the immune system to increase white - blood - cell count in the context of their main anti - cancer mechanism.

Answer:

1. A. DNA damage in a cell cannot be repaired at a cellular checkpoint.
2. D. Damaged DNA will remain unrepaired and a tumor may form.
3. D. PDGF binds to the surface of cells to promote tissue growth to close the wound.
4. B. Chemotherapy drugs work to disrupt the cell cycle of rapidly dividing cancer cells.