Cell cycle checkpoint regulation and intrinsic and extrinsic apoptosis pathways tested on USMLE Step 1.
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- What is the primary function of the G1 phase of the cell cycle?
- Cell growth and preparation for DNA synthesis.
- What is the primary event of S phase in the cell cycle?
- DNA replication (chromosome duplication).
- What is the primary function of G2 phase?
- Cell growth and quality control checks before mitosis.
- What occurs during M phase of the cell cycle?
- Mitosis (nuclear division) and cytokinesis.
- What is the G0 phase of the cell cycle?
- A quiescent state in which a cell has exited the cycle and is not actively dividing.
- What is the restriction point (R point)?
- A late G1 checkpoint after which the cell is committed to divide independent of further growth signals.
- What does the cyclin D-CDK4/6 complex do?
- Drives progression through G1 by phosphorylating the Rb protein.
- What does the cyclin E-CDK2 complex promote?
- The transition from G1 to S phase.
- What complex drives the transition from G2 to M phase?
- Cyclin B-CDK1, also called maturation-promoting factor (MPF).
- What does hypophosphorylated (active) Rb protein do?
- Binds E2F and blocks transcription of genes needed for S phase.
- What is the function of the E2F transcription factor?
- Drives transcription of genes needed for S phase entry once released from Rb.
- What triggers activation of the p53 tumor suppressor protein?
- Detection of DNA damage in the cell.
- What does p53 induce to halt the cell cycle at the G1/S checkpoint?
- p21, a cyclin-dependent kinase (CDK) inhibitor.
- What does the G1/S checkpoint monitor?
- Whether DNA is undamaged before replication begins.
- What does the G2/M checkpoint monitor?
- That DNA replication is complete and DNA is undamaged before mitosis begins.