Chapter 10: Cell Cycle Flashcards
one example of a model organism for cell cycle research is…
s. cerevisiae yeast
why is s. cerevisiae yeast a good model organism?
it has: many cells that can be easily visualized, cell cycle that can be paused at a specific phase, all cells can be synced to one phase, and mutations are easily generated
what are the two irreversible points of the cell cycle?
replication of genetic material (S phase)
seperation of the sister chromatids (anaphase and anaphase 2)
the cell cycle can be put on hold at specific points called checkponts (T/F)
true
what do checkpoints do?
check to make sure the process was done correctly
allows cells to respond to internal and external signals
prevents critical phases from beginning until the previous phase is completed correctly
what are the three checkpoints?
G1/S
G2/M
mitotic spindle
what happens during the G1/S checkpoint?
cell “decides” to divide
primary point for external signal influence
what happens during the G2/M checkpoint?
cell makes a commitment to mitosis
assesses success of DNA replication
what happens during the spindle checkpoint?
cell ensures that all chromosomes are attached to the spindle
during late metaphase
why would a cell arrest/stop at the G1/S checkpoint?
if DNA is damaged by radiation or chemicals
if the cell is nutritionally deficient or growth factors are absent
a cell would arrest at the G2/M checkpoint if DNA is replicated accurately in the S phase (T/F)
false
is accurate DNA replication essential for genetically identical daughter cells?
yes
how is the cell cycle directly regulated?
by an internal control system consisting of cyclins (proteins) and cyclin-dependent kinases (enzymes-Cdk)
what is Cdk?
a protein kinase
phosphorylates and regulates the activity of target proteins
Cdk stays active until cyclin is completely degraded
primary mechanism of cell cycle controls
Cdk becomes active when a cell synthesizes cyclin that binds to a cell receptor (T/F)
true
phosphorylation regulates proteins that initiate/regulate key events in the cell cycle (T/F)
true
what are the three classes of cyclin?
G1/S cyclin
S cyclin
M cyclin
which Cdk does G1/S cyclin bind to? when does it happen?
Cdk2
near the end of G1
required for transition from G1 to S and to commit to DNA replication
which Cdk does S cyclin bind to? when does it happen?
Cdk2
in the S phase
required for initiation of DNA replication and progression of the cell through the S phase
which Cdk does M cyclin bind to? when does it happen?
Cdk1
in G2
required for transition from G2 to M and the progression of the cell through mitosis
what is the possible fourth cyclin?
G1 cyclin
which Cdk does G1 cyclin bind to? where does it happen?
Cdk4 and Cdk6
before the G1/S transition
forms two cyclin-Cdk complexes
G1 cyclin is needed to move the cell through the G1 checkpoint (T/F)
true
the M cyclin-Cdk1 complex is also known as the _____-_______ ___________ _________
M-phase promoting factor (MPF)
what enzyme complex does MPF activate when chromosomes are correctly attached to mitotic spindle?
anaphase-promoting complex (APC)
what does APC do?
degrades an inhibiter of anaphase, leads to separation of sister chromatids
regulates to degradation of M cyclin, making Cdk1 to lose its activity
is Cdk activity also controlled by the pattern of phosphorylation?
yes
what was johnson and rao’s experiment?
fused human HeLa cells at different stages of the cell cycle (produced a single cell w 2 separate molecules)
determined whether one nucleus influenced the other in terms of progression through the cell cycle
result: molecules in the cytoplasm influence the stage of the cell cycle
what did the gorbsky experiment help us understand about chromosome movement during anaphase?
helped us understand how the chromosomes move during anaphase
conclusion: chromosomes move by sliding over/along kinetochore microtubules
what is another name for down syndrome?
trisomy 21
what happens to cell cycle regulation in cancer?
cancer is uncontrollable cell division
produces a tumor (large mass of cells)
cancer cells lose adhesions to other cells and are free to move throughout the body
oncogenes are what kind of gene?
cancer causing
hormones and growth factors act on the cell by _________ __________ _________.
signal transduction pathway
contact inhibition triggers external reaction pathways that inhibit division by arresting the cell cycle (T/F)
false. trigger internal reaction pathways
what happens to cells that are in contact with one another?
shunted to G0 phase and prevented from dividing
set up by starship
bonus
