Finals Flashcards
Where do cells commit to a full completion?
Between G1 and S
The period between one M phase and the subsequent M phase is called:
Interphase
Which of the following processes occurs only in S phase of the cell cycle?
DNA replication
What happens during G1 in the cell cycle of a proliferating cell?
The cell makes more proteins, lipids, etc. and grows in size
Cyclins are needed to activate Cdks, but Cdk activity is not directly correlated with cyclin levels. Why?
Cdks are also regulated by phosphorylation.
Levels of M-cyclins rapidly drop towards the end of mitosis, so that the M-Cdk becomes inactive. What is the cause for this dramatic decrease in cyclin expression?
Increased rate of protein degradation
Platelet-derived growth factor (PDGF) is a mitogen that activates tyrosine kinase receptors and this leads to the proliferation of cells. Signaling downstream from the PDGF receptor does what to stimulate proliferation?
Phosphorylates the Rb protein to relieve inhibition of cell proliferation genes
The cell-cycle control system uses Cdk inhibitor proteins:
To arrest the cell cycle at specific transition points.
The protein p53 is an important tumor suppressor that arrests the cell cycle if DNA is damaged. P53 functions by
Turning on the transcription of a protein that binds to and inhibits Cdks.
Which statement is true about M-Cdks?
Activation of M-Cdk determines if/when M phase is initiated.
Why is cell division important?
Reproduction, development of multicellular organism, cell replacement (injured or worn out cells)
What happens in mitosis?
Nuclear division
What happens in cytokinesis?
Cytoplasmic division
What happens in G1?
Some growth (non dividing cells will revert to G0)
What happens in S?
DNA replication
What happens in G2?
Growth
What is MPF?
Cyclin-Cdl complex
What might lead to increased levels of cyclin?
Increased levels of transcription/translation or decreased degradation
How might the rapid decrease in cyclin be accomplished?
Ubiquitin addition and degradation by proteasomes
Why doesn’t MPF activity mirror changes in cyclin levels?
Has to be phosphorylated correctly
What are questions at G2 checkpoint?
Is all DNA replicated? Is all DNA damage repaired
What are questions in mitosis checkpoint?
Are all chromosomes attached to mitotic spindle?
What are questions in G1 checkpoint?
Is environment favorable for S phase?
What is inhibition between G2 and M?
Inhibition of activating phosphatase (Cdc25) blocks entry to mitosis