L 4: Radiosensitivity and Cell age in mitotic age Flashcards
What is used to identify cells in S phase?
Bromo-deoxy-uridine
Cells used in Vitro
- He-La cells (cell cycle time: 24 hrs)
- Chinese hamster cells ( cell cycle time: 11 hrs)
- G1 phase is the variable phase in the cell cycle
Phases of cell cycle
M: Mitosis
S: Synthesis
G1/G2: Gap phase
G0: Cell cycle arrest
M -> G1 -> S -> G2
Time in each phase of the cycle
Most time spent in Sphase
Regulation of cell cycle
- Occurs by activation of cyclin dependent kinases CDK
- They posphyrlate to several protein substrates that drive cell cycle events for initiation of mitosis.
CDk cyclins are inactivated by
- Phosprylation in adenosine triphosphate binding domain.
- inhibitory proteins.
- Ubiquitin mediated degradation of cyclin subunit.
Mitotic Harvest
Hydroxyurea
- Kills the cells in S phase
- Blocks the cells entering to G1 phase.
Cells in which part of cell cycle are radiation sensitive?
M/G2
Cells in which part of the cell cycle are radiation resistent?
late S
Cell cycle is controlled by?
Molecular checkpoint genes
OER
Oxygen Enhancement Ratio
M Phase
Approx 1 hour
Most Radio resistent Phase
Board question
G-0 Phase!!
R Point
- Late in G1 Phase
- Not related to check points
Most variable phase in cell cycle
Board question
G1 Phase!
Bromo-deoxy-uridine
- Radiosensitizer
- Monitor cells in the cell cycle
- Commonly used as no need for spl radio label, no radio activity, shorter time: can detect right away.
Interphase
Includes phases G1, S, G2.
Flow Cytometry
Board Question
Summary of the chapter
