Flashcards in cell cycle control Deck (52):
What doe half the cell cycle constitute?
How long is M phase?
a short time
What is M phase responsible for?
What happens in the S phase?
synthesis of DNA
What takes place in mitosis?
What are the phases of mitosis?
What is the state of the chromosomes in interphase?
the are unwinded and they can hardly be seen
What happens in interphase right before Mphase begins?
chromosomes start to condense
When does the nuclear envelope breaks up?
When does the chromosomes associate their kinetichores with mitotic spindles?
what happens in metaphase?
chromosomes line up at the equator
what happens in anaphase?
sister chromatids are pulled apart to opposite ends
What is the metaphase to anaphase transition?
the glue that holds the sister chromatids together disintegrates
What happens in telophase?
contractile ring of actin and myosin forms
nuclear membrane starts to reform
What happens in cytokinesis?
Cytoplasm is split into two
What phase is cell growth and accumulation of cell mass?
What are the four sequential phases?
What is the G0 phase?
if conditions are not right for dividing cells stay in this phase. can extend for an indefinite period
Why are yeast the model system to study the cell cycle?
Genome size 1% of humans
amendable to genetic manipulations
can proliferate in the haploid state
What did mutations of the yeast genome allow for the discovery of?
Cell division cycle genes (Cdc genes)
How are Cdc mutants cell cycle studied?
They were arrested at different points in the cell cycle
How are Cdc mutants arrested?
There are temperature sensitive mutants established.
They can grow at permissive temps then change the temp and the cell will stop at that point in the cell cycle
What cells can you use to analyze the cell cycle and why?
100000 times more cytoplasm than humans/easy ti inject test substance in large xenopus eggs
When does rapid cell division occurs in Xenopus eggs?
early in embryogensis without growth signals and control mechanisms of other complex cell cycles
How can you look at the cell cycle progression?
under the microscope (mitosis, cytojinesis)
DNA binding stains or specific antibodies(reveal condensation state)
What is a sphase identifier?
incorporation of BrdU
How can you measure DNA content?
DNA binding dyes and flow cytometry
What are the major regulatory transition points?
Start or restriction point
Metaphase - to anaphase
What else is flow cytometry known as?
Fluorescence activating cell sorting (FACS)
When is the start checkpoint?
at the end of G1 right before S phase
What is the cell checking for at the the start checkpoint?
is the environment correct to proceed int o S phase
it is a restriction point. once past this point cannot turn around
When is the G2/M phase checkpoint?
end of G2 before Mphase
What is the cell checking for at the G2/M phase check point?
is all DNA replicated
is environment favorable
What is the cell checking for at the Metaphase to anaphase transition?
are all the chromosomes attached to the spindle
If all the chromosomes are attached to the spindle what does it trigger?
trigger anaphase to and proceed to cytokinesis
What are the regulators of of the cell cycle?
Cyclin dependent kinases (Cdks)
they are activated by cyclin binding
What protein regulate Cdks?
What are the different cyclins?
When are G1/S cyclins active?
When S cyclins actives?
start point until mitosis
When are M cyclins active?
at G2/M phase
When are G1 cyclins active?
G1 through start point
What protein is active at the anaphase to metaphase transition point?
anaphase promoting complex/cyclosome (APC/C)
What are APC/C involved in?
degradation of M cyclins
How are Cdks activated?
1) cyclin binding (exposes active site)
2)Cdk activating kinase (phosphorylates Cdks)
How are Cdks inactivated?
1) Wee1 kinase (adds two inhibitory phosphates)
What removes the Wee1 inhibitory phosphate?
What are CKIs?
Cdk inhibitory protein
p27 is one type
p21 is one type
When is the Cdk inactive?
no cyclin bound
active site blocked
when is the Cdk partly activated?
When the cyclin binds and the active site block forms a t loop
When is Cdk fully activated?
phosphorylation of the binding site by Cdk activating protein