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Post on 02-Jan-2016
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--Background on Werner’s syndrome --Hayflick
His persistence and his ‘limit’ -- Theories of cellular aging -- Introduction to the cell cycle
Now: -- More Cell Cycle
How is it controlled? Checks and BalancesBalancing cell proliferation and cell death
Previously:
Basic controls neededclock/timer mechanismensure correct order of eventswork like binary switchesadaptability
Why are these characteristics important?
Khodjakov & Rieder and ‘checkpoints’–They aren’t something that is ‘activated’. The security system is always on — ‘normal’ range of activity and even quick fixes that reset are allowed
What needs to be checked for?Externally?
presence of nutrientspresence of spacepresence of cell growth signalsabsence of inhibitory signals
Internally?removing negative blocksactivation of steps by
particular complexeschecking for damage before continuing
Mitotic checkpoint and chromosome #
Why/How could this be more effective thanusing an accumulation of positive signals?
Sometimes going forward requires silencing the negative
Sometimes checkpoints require particular combinations
Figure 17-16Figure 17-17
Complex can only be active when together.Complex only together when cyclins present. And cyclins……cycle.
CAK (Cdk activating kinase) and CKI (cyclin kinase inhibitors) act on formed
complexes to regulate function
Regulating the complex
How do you make or get rid of the complex– (cycling the cyclins to ‘off’)
Transcriptional control
Degradation controlUbiquitinationProteasome
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