Cell cycle and proliferation signaling MCQs With Answer

Cell cycle and proliferation signaling MCQs With Answer

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Cell cycle and proliferation signaling MCQs With Answer

This quiz compilation is designed for M.Pharm students to deepen their understanding of cell cycle control and proliferation signaling pathways relevant to drug discovery and therapeutics. The questions explore molecular regulators such as cyclins, cyclin-dependent kinases (CDKs), checkpoint proteins (p53, Rb), ubiquitin ligases (APC/C, SCF), and key signaling cascades (RTKs, Ras/MAPK, PI3K/AKT/mTOR). Emphasis is placed on mechanisms of checkpoint activation, replication licensing, spindle assembly, senescence, and pharmacological modulation by targeted inhibitors. Each question includes a concise answer to reinforce learning for advanced coursework, exam preparation, and translational research contexts.

Q1. Which cyclin-CDK complex is primarily responsible for driving cells from G1 phase into S phase?

  • Cyclin B–CDK1
  • Cyclin A–CDK2
  • Cyclin D–CDK4/6
  • Cyclin E–CDK1

Correct Answer: Cyclin D–CDK4/6

Q2. The retinoblastoma protein (Rb) controls the G1/S transition primarily by regulating which transcription factors?

  • STAT family
  • E2F family
  • NF-κB family
  • SMAD family

Correct Answer: E2F family

Q3. Which ubiquitin ligase complex targets mitotic cyclins for degradation to allow anaphase progression?

  • SCF (Skp1–Cullin–F-box)
  • MDM2
  • APC/C (Anaphase-Promoting Complex/Cyclosome)
  • Cullin 3–KEAP1

Correct Answer: APC/C (Anaphase-Promoting Complex/Cyclosome)

Q4. Activation of which kinase is an early response to single-stranded DNA and replication stress, coordinating S and G2 checkpoints?

  • ATM
  • ATR
  • PKA
  • mTOR

Correct Answer: ATR

Q5. p21 (CDKN1A) inhibits cell cycle progression mainly by binding to and inhibiting which proteins?

  • Cyclin-dependent kinases (CDKs)
  • Ubiquitin ligases
  • Phosphatases like PP2A
  • Telomerase components

Correct Answer: Cyclin-dependent kinases (CDKs)

Q6. Which signaling pathway is most directly associated with nutrient sensing and regulation of protein synthesis to support cell growth and proliferation?

  • Notch signaling
  • PI3K–AKT–mTOR pathway
  • JAK–STAT pathway
  • Wnt/β-catenin pathway

Correct Answer: PI3K–AKT–mTOR pathway

Q7. The spindle assembly checkpoint (SAC) delays anaphase until which condition is satisfied?

  • DNA replication is complete
  • All kinetochores are properly attached to spindle microtubules
  • Centrosome duplication has initiated
  • Cellular ATP levels rise above threshold

Correct Answer: All kinetochores are properly attached to spindle microtubules

Q8. Which tumor suppressor kinase is primarily activated by double-strand DNA breaks and coordinates cell cycle arrest and DNA repair?

  • Chk1
  • ATM
  • ATR
  • mTOR

Correct Answer: ATM

Q9. Cyclin-dependent kinase inhibitors like palbociclib target which CDKs to treat certain breast cancers?

  • CDK1/2
  • CDK4/6
  • CDK7/9
  • CDK11/12

Correct Answer: CDK4/6

Q10. Origin licensing for DNA replication in G1 requires loading of which multiprotein complex onto replication origins?

  • PCNA–RFC complex
  • MCM2–7 helicase complex
  • ORC–Cdc6–Cdt1 pre-replicative complex
  • DNA polymerase α–primase complex

Correct Answer: ORC–Cdc6–Cdt1 pre-replicative complex

Q11. Which oncoprotein directly activates transcription of cyclin D and many genes promoting cell cycle entry downstream of mitogenic RTK signaling?

  • p53
  • c-Myc
  • Rb
  • BRCA1

Correct Answer: c-Myc

Q12. Loss of function of p16INK4a primarily leads to uncontrolled activity of which kinase complex?

  • Cyclin E–CDK2
  • Cyclin B–CDK1
  • Cyclin D–CDK4/6
  • AMPK

Correct Answer: Cyclin D–CDK4/6

Q13. Which assay is commonly used to detect proliferating cells in tissue sections by marking cells in S-phase?

  • TUNEL assay
  • BrdU incorporation assay
  • Annexin V staining
  • Comet assay

Correct Answer: BrdU incorporation assay

Q14. Oncogenic Ras mutation commonly promotes proliferation through persistent activation of which downstream cascade?

  • MAPK/ERK pathway
  • Notch pathway
  • Hedgehog pathway
  • p38 MAPK stress pathway

Correct Answer: MAPK/ERK pathway

Q15. Telomerase reactivation in cancer cells primarily allows cells to bypass which cellular process that limits replicative potential?

  • Autophagy
  • Apoptosis
  • Senescence / replicative crisis due to telomere shortening
  • Necrosis

Correct Answer: Senescence / replicative crisis due to telomere shortening

Q16. SCF (Skp1–Cullin–F-box) complexes mediate ubiquitination of cell-cycle regulators; substrate recognition is conferred mainly by which component?

  • Skp1
  • Cullin
  • F-box protein
  • Rbx1

Correct Answer: F-box protein

Q17. Which checkpoint kinase phosphorylates and inactivates Cdc25 phosphatases, contributing to cell cycle arrest after DNA damage?

  • Chk1 and Chk2
  • CDK7
  • mTORC1
  • ERK1/2

Correct Answer: Chk1 and Chk2

Q18. Contact inhibition of proliferation in normal epithelial cells is largely mediated through which pathway that senses cell–cell adhesion?

  • Hippo pathway
  • PI3K pathway
  • NF-κB pathway
  • HIF pathway

Correct Answer: Hippo pathway

Q19. Which proliferation marker is detected by antibody staining and is expressed in all active phases of the cell cycle but absent in G0?

  • Caspase-3
  • Ki-67
  • p27Kip1
  • γ-H2AX

Correct Answer: Ki-67

Q20. Inhibitors of mTOR are used to suppress cell proliferation; which immediate downstream effect is most associated with mTORC1 inhibition?

  • Increased cyclin D translation
  • Enhanced protein synthesis via S6K and 4E-BP1 inhibition
  • Reduced cap-dependent translation through decreased S6K activity and hypophosphorylated 4E-BP1
  • Activation of Ras signaling

Correct Answer: Reduced cap-dependent translation through decreased S6K activity and hypophosphorylated 4E-BP1

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