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Biosystems II
Cell Cycle
23
Biology
Graduate
02/09/2012

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Term
G1
Definition
-"resting phase"
-cell makes enzymes needed for DNA synthesis
-cells spend most of cell cycle in this phase
-varies most amoung cell types
-cell mass gradually increases
-most DNA content?
Term
S
Definition
-chromosome duplication
Term
G2
Definition
-protein synthesis
-opportunity for DNA repair
Term
M
Definition
-mitosis (nuclear division)
-cytokinesis (cytoplasmic division)
Term
time in S and M phase
Definition
12-24 hours
Term
After M phase
Definition
-continute to G1
-differentiate into specialized cells
-enter G0 phase
Term
cyclins and cdks
Definition
-found in cytoplasm
-cyclins activate cdks
Term
cdk levels are constant throughout cell cycle?
Definition
yes
Term
cdk activity at G1
Definition
-essentially zero
Term
determine if cell can pass checkpoint
Definition
-number of complexes
Term
CAK
Definition
-phoshorylates/activates cdk
Term
Wee kinase
Definition
-phosphorylates/inhibits cdk
Term
cdc25
Definition
-can remove 2nd phosphate group (caused by Wee kinase)
Term
p27 (CKI)
Definition
-inhibits/causes rearrangement of cdk active site
Term
quantity control of cyclins and CKIs
Definition
-ubiquitin labels for degradation
Term
determines whether cells progresses to next checkpoint
Definition
number of active complexes
Term
determines number of active complexes
Definition
-cyclin and CKI concentration
-action of kinases/phosphatases
Term
cyclin and CKI levels determined by
Definition
ubiquitinylation and synthesis
Term
synthesis determined by
Definition
growth factor and mitogen
Term
control of S phase
Definition
-pre-RCs form during G1
-S-cdk triggers DNA replication
-preinitiation complex forms
-activation of replication origins causes disassembly of pre-RCs
-pre-RCs cannot reform until G1
-because pre-RC formation is stimulated by APC and inhibited by cdks
Term
euchromatin
Definition
open structure, genes can be expressed
Term
heterochromatin
Definition
condensed structure, genes cannot be expressed
Term
cohesions
Definition
link sister chromatids
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