Cell bio 406 lecture 10
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Cell bio 406 lecture 10
Cellular Biology 406 Cell cycle cell division
cell cycles and division
What is the cell cycle?
series of events leading to cell division, composed of growth, synthesis, and mitosis.
What is G1 of the cell cycle?
cellular contents excluding chromosomes are duplicated?
What is the S phase?
each of the 46 chromosomes are duplicated.
What is the G2 phase?
Cell double checks the duplicated chromosomes for error and makes any necessary repairs.
What is G0 phase?
cell cycle arrest
How is mitosis characterized?
by location and behavior of chromosomes.
How is mitosis separated?
karyokinesis and cytokinesis.
What is the most important kinase in mitosis?
cyclin B/CDK1 complex- the master mitotic regulator
When are chromosomes visible?
during mitosis NOT INTERPHASE
What mediates chromatin condensation?
condensin- a complex of several proteins that bind and encircle DNA forming loops and coils
What aids in chromosome separation?
the mitotic spindle
What are spindles?
bipolar arrays of microtubules composed of tubulin
What nucleates teh growth of the spindle microtubules?
Where do spindles attach?
at the chromosomes kinetochores in the most contricted region of the chromosome (the centromere)
Where does the centrosome nucleate?
the - end
Where does the microtubule attach?
the + end attaches to the kinetochore on the centromere
What are the 5 phases of mitosis?
prometaphase, metaphase, anaphase, and telophase
What occurs during prophase?
chromosomes coil and supercoil
What happens during prometaphase?
nuclear envelope breaks down and kinetochore microtubules appear
What happens during metaphase?
What happens during anaphase?
sister chromatids separate
What happends during telophase?
daughter chromosomes reach poles and nuclear envelop/nucleoli reform
what is endoreduplication?
replication of hte genome without cell division or cytokinesis
What are the types of endoreduplication?
endocycle and endomitosis.
Why is endoreduplication necessary?
the need to increase cell size or if that cell needs a lot of genetic information in order to respond to stress signals.
What happens if cell cycle progression is defective?
p53 is activated leading to cell cycle arrest, DNA repair, apoptosis, or senescence
What is myc?
a transcription factor downstream of RTKs that promotes proliferation when activated and is involved in disease and development.
What is the G1 checkpoint?
is environment favorable?
What is G2 checkpoint?
is all DNA replicated and is environment favorable
What is M checkpoint?
are all chromosomes attached to the spindle
How do checkpoints generally operate?
through negative intracellular signals
What happens if a checkpoint is inactive?
Cell cycle progesses even with errors
What are CDKs and what do they do?
Cyclin-dependent kinases regulate cell cycle.
How are CDKs activated?
when complexed with a cyclin protein
How does CDK control the cell cycle?
associating with different cyclins to trigger different events
What terminates CDK function?
What do G1 and S cyclins do?
bind CDKs at the end of G1 and commit the cell to DNA replication.
What do S-cyclins do?
bind CDKs during S phase and are required for initation of DNA replication.
What do M cyclins do?
promote the events of mitosis
How are CDK-cyclin complexes regulated?
phosphorylation, inhibitory proteins, proteolysis, ad subcellular localization
What does CAK do?
phosphorylates CDK1 to activate CDK1-CyclinB complex
What does Wee1 do?
phosphorylates CDK1 to inactivate the CDK1-Cyclin B complex at G2.
What does CDC25 do?
Reverse Wee1 phosphorylation to allow G2 to M transition.