Lecture 6 Flashcards
(40 cards)
The cell-cycle control system depends on _________
cyclically activated cyclin-
dependent kinases (Cdks)
true/false: Cyclins have no enzymatic activity
true
A ______ is a protein that adds a phosphate to other
proteins; the activity of the target protein is modified
kinase
cyclins and cell cycle kinases bind to become ___________ active
enzymatically
true/false: Cyclin levels rise and fall in a cyclical fashion throughout cell cycle
true
_____ triggers entry into
the M phase from G2 by
forming the _____ complex
M cyclin
M-Cdk
_______ and _______ help
launch the S phase by
forming ______ and _______
complexes
S cyclin and G1/S cyclin
S-Cdk and G1/S-Cdk
_____ form ______,
helping to drive the cell
through G1 toward the S
phase
G1 cyclins
G1-Cdks
_________ in cyclin concentration - transcription of cyclin genes and
synthesis of cyclin proteins
increase
_______ in cyclin concentration - targeted destruction of the
protein
Rapid fall
how does a protein get marked for desctruction?
by getting tagged with ubiquitin by APC/C
_____ concentrations increase gradually.
The activity of _________ are
turned on abruptly
Cyclin
the cyclin–Cdk complexes
What triggers the abrupt activation of cyclin Cdk
complexes?
Protein kinases and phosphatases act together
to regulate the activity of specific cyclin–Cdk
true/false: Cyclin-Cdks catalyze the phosphorylation
and activation of hundreds of different
target proteins in the cell
true!
true/false: cyclin-cdks shut down the protein phosphatase
that opposes its activity
true!
G1-to-S transition: Cdk inhibitors keep
cells from entering S phase
G2-to-M transition: Activation of M-Cdk is
inhibited by inhibiting the phosphatase
Delay the exit from mitosis: Inhibiting
APC/C and preventing the degradation of
M cyclin
are all ways to _________
pause the cell cycle
to pause the cell cycle-
what happens at the G1-to-S transition: _________
Cdk inhibitors keep
cells from entering S phase
to pause the cell cycle-
what happens at the G2-to-M transition: _________
Activation of M-Cdk is
inhibited by inhibiting the phosphatase
to pause the cell cycle-
what happens to delay the exit from mitosis: _________
Inhibiting
APC/C and preventing the degradation of
M cyclin
DNA damage in G1 causes an increased concentration and
activity of _______
protein p53
protein p53 activates the gene encoding a protein called _____ (a Cdk inhibitor)
p21
true/false: The p21 protein binds to G1/S-Cdk and S-Cdk, preventing them from driving the cell into the S phase
true
what happens when the p53 protein is defective?
It can lead to a higher rate of mutations in cells and the
formation of cancerous cells
50% of human cancers cells have mutations in p53 gene
Defects in cell cycle genes can cause cancer
what drives the entry into mitosis?
M-Cdk
