1. What is the main role of the G1 checkpoint in the cell cycle?
A) To ensure DNA replication occurs
B) To check for DNA damage before cell division
C) To ensure proper chromosome segregation
D) To check for proper spindle formation
Answer: B) To check for DNA damage before cell division
2. Which protein is primarily involved in regulating the G1 checkpoint?
A) Cyclin D
B) Cyclin A
C) Cyclin E
D) p53
Answer: D) p53
3. What does the G2 checkpoint ensure before cell division?
A) That the cell has sufficient energy reserves
B) That DNA replication is complete and error-free
C) That the cell has doubled in size
D) That the chromosomes are properly aligned
Answer: B) That DNA replication is complete and error-free
4. Which of the following proteins is a tumor suppressor involved in the regulation of the G1 checkpoint?
A) Cyclin D
B) Retinoblastoma (Rb)
C) p21
D) Cyclin B
Answer: B) Retinoblastoma (Rb)
5. What role does cyclin-dependent kinase (CDK) play in the cell cycle?
A) It initiates DNA replication
B) It phosphorylates target proteins to drive the cell cycle forward
C) It repairs DNA damage
D) It prevents apoptosis
Answer: B) It phosphorylates target proteins to drive the cell cycle forward
6. Which of the following is true of the role of p53 in cell cycle regulation?
A) It promotes cell division under stress
B) It prevents apoptosis during DNA damage
C) It induces apoptosis if DNA damage is irreparable
D) It enhances cyclin expression
Answer: C) It induces apoptosis if DNA damage is irreparable
7. The restriction point in the G1 phase is controlled by which protein?
A) p53
B) Cyclin D
C) Cyclin E
D) p21
Answer: B) Cyclin D
8. In which phase of the cell cycle is the spindle assembly checkpoint active?
A) G1
B) S
C) G2
D) M
Answer: D) M
9. How does the spindle assembly checkpoint prevent incorrect chromosome segregation?
A) By halting the cell cycle until spindle microtubules are properly attached
B) By preventing DNA replication
C) By activating the p53 protein
D) By increasing cyclin levels
Answer: A) By halting the cell cycle until spindle microtubules are properly attached
10. Which of the following is an example of a cyclin-CDK complex?
A) Cyclin A – CDK2
B) p21 – CDK
C) Cyclin B – Rb
D) p53 – CDK1
Answer: A) Cyclin A – CDK2
11. Mutations in which gene are commonly associated with many types of cancer?
A) Rb
B) p53
C) CDK1
D) Cyclin A
Answer: B) p53
12. What happens when the p53 gene is mutated in a cell?
A) The cell becomes immortal and continues to divide uncontrollably
B) The cell undergoes apoptosis as soon as damage is detected
C) The cell enters a permanent state of dormancy
D) The cell increases its sensitivity to chemotherapy
Answer: A) The cell becomes immortal and continues to divide uncontrollably
13. What is the role of the retinoblastoma protein (Rb) in cell cycle regulation?
A) It induces DNA replication during the S phase
B) It inhibits the cell cycle at the G1 checkpoint by preventing E2F activity
C) It activates the G2 checkpoint
D) It accelerates chromosome segregation during mitosis
Answer: B) It inhibits the cell cycle at the G1 checkpoint by preventing E2F activity
14. Which of the following is a characteristic of cancer cells?
A) They are sensitive to the G1 checkpoint
B) They exhibit uncontrolled cell division
C) They require normal levels of cyclins for division
D) They rely on the G2 checkpoint for accurate division
Answer: B) They exhibit uncontrolled cell division
15. What is the function of the p21 protein in the cell cycle?
A) To promote the activation of cyclins
B) To inhibit CDKs and halt the cell cycle in response to DNA damage
C) To enhance apoptosis during stress
D) To stimulate DNA replication
Answer: B) To inhibit CDKs and halt the cell cycle in response to DNA damage
16. What is a common result of mutations in tumor suppressor genes like Rb and p53?
A) Increased apoptosis
B) Decreased cell proliferation
C) Uncontrolled cell growth and cancer development
D) Increased cell differentiation
Answer: C) Uncontrolled cell growth and cancer development
17. Which of the following events is triggered at the G2 checkpoint?
A) DNA repair or apoptosis
B) Cyclin D activation
C) Activation of the mitotic spindle
D) Inhibition of the G1/S transition
Answer: A) DNA repair or apoptosis
18. What is the primary cause of cancer in terms of the cell cycle?
A) Mutation in proto-oncogenes
B) Disruption of the M phase
C) Unregulated apoptosis
D) Uncontrolled activation of cyclins and CDKs
Answer: D) Uncontrolled activation of cyclins and CDKs
19. The “checkpoint failure” hypothesis of cancer suggests that
A) Mutations in DNA repair enzymes lead to cancer
B) Cells cannot progress past checkpoints, thus avoiding division
C) The cell cycle progresses without proper regulation or checkpoints
D) Cells only divide when DNA is properly replicated
Answer: C) The cell cycle progresses without proper regulation or checkpoints
20. What is the effect of high cyclin D levels on the cell cycle?
A) Inhibition of CDK activity
B) Induction of G1 arrest
C) Activation of CDK4/6, pushing the cell cycle past the G1 checkpoint
D) Deactivation of mitotic progression
Answer: C) Activation of CDK4/6, pushing the cell cycle past the G1 checkpoint
21. Which type of gene mutation can activate proto-oncogenes into oncogenes?
A) Loss-of-function mutations
B) Gain-of-function mutations
C) Methylation mutations
D) Frameshift mutations
Answer: B) Gain-of-function mutations
22. What is a common effect of mutations in the p53 gene?
A) Inability to repair damaged DNA
B) Increased cell differentiation
C) Inhibition of mitosis
D) Decreased cancer cell migration
Answer: A) Inability to repair damaged DNA
23. Which phase of the cell cycle is controlled by the mitotic spindle checkpoint?
A) G1
B) G2
C) M (Metaphase to Anaphase transition)
D) S
Answer: C) M (Metaphase to Anaphase transition)
24. Which of the following proteins helps prevent the formation of tumors by regulating the G1/S transition?
A) Cyclin D
B) p53
C) Cyclin B
D) CDK2
Answer: B) p53
25. In cancer cells, what is often altered in relation to the cell cycle?
A) Normal function of tumor suppressors and CDKs
B) Mutations in growth factors that inhibit cyclin production
C) Reduced activity of cyclin-dependent kinases
D) Unregulated and excessive activity of CDKs and cyclins
Answer: D) Unregulated and excessive activity of CDKs and cyclins
26. Which of the following best describes a tumor suppressor gene?
A) It encourages cell proliferation
B) It acts to prevent excessive cell division
C) It increases cell division in response to stress
D) It converts proto-oncogenes into oncogenes
Answer: B) It acts to prevent excessive cell division
27. How does chemotherapy target cancer cells at the cell cycle level?
A) By enhancing cyclin activity
B) By blocking DNA replication or mitosis
C) By inducing apoptosis in healthy cells
D) By activating proto-oncogenes
Answer: B) By blocking DNA replication or mitosis
28. Which of the following mutations are often found in cancer cells regarding cell cycle regulation?
A) Overexpression of tumor suppressors
B) Loss of CDK inhibitors
C) Mutations in the mitotic spindle checkpoint proteins
D) Increased p53 activity
Answer: B) Loss of CDK inhibitors
29. What is the effect of p16INK4a on the cell cycle?
A) It activates CDK2 to promote cell division
B) It inhibits CDK4 and CDK6, preventing progression from G1 to S phase
C) It promotes the G2 checkpoint
D) It accelerates cell cycle progression
Answer: B) It inhibits CDK4 and CDK6, preventing progression from G1 to S phase
30. Which of the following is a hallmark feature of cancer cells related to cell cycle regulation?
A) Strict control of CDK activation
B) Increased sensitivity to apoptosis
C) Defects in checkpoint control and regulation
D) Dependence on normal tumor suppressor function
Answer: C) Defects in checkpoint control and regulation
These questions provide a comprehensive overview of key aspects of cell cycle regulation, checkpoints, and their link to cancer.
