tumour pathology 4 Flashcards
what is a cell cycle?
the interval between mitotic divisions
what are the phases of the cell cycle, and what happens in each?
- G1 - synthesis of components required for DNA synthesis
- S - DNA synthesis
- G2 -preparation for mitosis
- M - mitosis and cell division
G0- extension of G1, quiescent state, dormant
when does DNA repair occur?
G2 phase
when can the cell cycle be affected by external factors?
in the G1 phase
examples of external factors
hormones, cytokines, growth factors, stroma
where are the checkpoints of the cell cycle?
- G1 checkpoint at the G1/S transition
- G2 checkpoint at -the G2/M transition
- M checkpoint between metaphase and anaphase
where is the cell cycle arrested if cell size is inadequate?
G1 or G2
where is the cell cycle arrested if nutrient supply is inadequate?
G1
where is the cell cycle arrested if essential external stimuli are lacking?
G1
where is the cell cycle arrested if DNA is not replicated?
S
where is the cell cycle arrested if DNA is damaged?
G1 or G2
where is the cell cycle arrested if chromosomes mis-align
M-phase
how do checkpoints work?
- cyclin dependent kinases are present in the cell
- cyclin levels rise if the checkpoint has the go-ahead.
- these bind to CDKs, activating them.
- the active CDKs then act by phosphorylating sybstrates
- these phosphorylated substrates are required for the next stage of the cell cycle
the cell cycle is also regulated using CDK inhibitors
what does INK4A inhibit?
CDK4
INK4A inhibitors
p16^INK4A
p15^INK4B
p18^INK4C
p19^INK4D