The Cell Cycle Regulation Flashcards
Two basic parts comprise the cell cycle.
Mitosis and Interphase
is the most dramatic stage of
the cell cycle.
Mitosis or Nuclear Division
It is the time when the separation of daughter
chromosomes occurs and usually ends with cell division
or cytokinesis.
Mitosis or Nuclear Division
A typical eukaryotic cell represented by a
human cell in culture divides approximately
Blank.
every 24 hours.
Mitosis and cytokinesis last for approximately an
hour, so about 95% of the cell cycle is spent in
Blank, the period between Blank.
interphase and mitoses.
the chromosomes are
decondensed and distributed throughout the
nucleus, so the nucleus appears morphologically
uniform.
interphase
at the Blank level, interphase is the
time during which both DNA replication and cell
growth occur as the cell prepares to divide
molecular
The cell maintains its growth rate throughout the
?
interphase
is synthesized during only a portion of
the interphase.
DNA
DNA synthesis divides the cycle of eukaryotic cells into
four discrete phases.
- M phase, G1 phase (gap 1), S phase, and G2 phase (gap 2).
The Blank of the cell cycle is the period
when mitosis occurs.
* This is usually followed by cytokinesis.
M phase
The mitotic phase is further divided into 4
major phases that include
Prophase, Metaphase, Anaphase, and Telophase.
is the one that follows the M
phase, which corresponds to the interval
(gap) between mitosis and initiation of
DNA replication.
G1phase
is the synthesis phase following
G1. During this phase, DNA replication
takes place.
S phase
follows the completion of DNA
synthesis. During this phase, the proteins
are synthesized in preparation for
mitosis.
G2 phase
from the environment regulate the progression
of cells through the division cycle.
Extracellular signals
monitor and coordinate the various processes that take place during different cell cycle phases.
Internal signals
An example of cell cycle regulation by
extracellular signals is provided by the
effect of Blank on animal cell
proliferation
growth factors
TRUE OR FALSE
Also, various cellular processes that occur in cells, such
as growth, DNA replication, and mitosis, must not be
coordinated during the progression of the cell cycle.
False (must be coordinated)
What are these regulatory transitions?
- Start (or the restriction point) in late G1
- G2/M transition.
- Metaphase-to-anaphase transition
In eukaryotic cells, the Blank generally governs cell-cycle
progression at three major regulatory
transitions
cell-cycle control system
- Cell commits to cell-cycle entry
and chromosome duplication. - is controlled by external signals
such as the availability of
nutrients, as well as by cell size.
Start (or the restriction point) in
late G1.
- Control system checks if all DNA has
been replicated already and if the
environment is favorable for nuclear
division and triggers the early mitotic
events that lead to chromosome
alignment on the mitotic spindle in
metaphase. - Checks if all DNA has been replicated
already and if the environment is
favorable to proceed to the next phase
of the cycle.
G2/M transition.
- Control system checks if all
chromosomes are already
attached to the spindle and
stimulate sister-chromatid
separation, leading to the
completion of mitosis and
cytokinesis
Metaphase-to-anaphase
transition
If problems are detected inside or outside of the
cell, Blank blocks progression
through each of the transitions.
the control system
Two important checkpoints in eukaryotic cells ensure that complete genomes are transmitted to daughter cells:
- DNA damage checkpoints
- spindle assembly checkpoint
- Ensure that damaged DNA is not
replicated and passed on to
daughter cells. - Sense damaged or incompletely
replicated DNA and coordinate
further cell cycle progression with
the completion of DNA replication
or repair. - function in G1, S, and G2 and lead
to cell cycle arrest in response to
damaged or unreplicated DNA.
DNA damage checkpoints
Such arrested cells then enter a
Blank of the cell cycle called
G0, in which they can remain for long
periods of time without proliferating.
* cells are metabolically active,
although they cease growth and have
reduced rates of protein synthesis
G0 or quiescent stage
- maintains the integrity of the
genome occurring towards the
end of mitosis. - sees to it that the alignment of
chromosomes on the mitotic
spindle is successful. - ensure that a complete set of
chromosomes is distributed
accurately to the daughter cells.
Spindle assembly checkpoint
The two key components of the cell
cycle control system are the?
cyclin and the cyclin-dependent kinases
(Cdks).
In the presence of unattached or
misattached kinetochores (red circle),
the spindle assembly checkpoint is
turned on (SAC ON) and the kinetochore
proteins Blank, Blank, Blank, Blank assemble at the cytosol to form the Blank.
Once the MCC is generated, the CDC20
becomes unable to bind to the Blank, leading to mitotic arrest at the metaphase to anaphase transition.
BUB3, BUBR1, MAD2 and
CDC20
mitotic checkpoint complex (MCC)
anaphase-promoting
complex/cyclosome (APC/C)
TRUE OR FALSE
Without cyclin, Cdk is active
False (inactive)
Cyclins are of four classes
G1/S cyclins
S-cyclins
M-cyclins
G1-cyclins
activate Cdks in late G1 and thereby
trigger progression through Start, resulting in the
commitment to cell-cycle entry.
* Their levels fall in the S phase.
G1/S-cyclins
are those that bind Cdks soon after
progression through Start and help stimulate
chromosome duplication.
S-cyclins
are those that activate Cdks that
stimulate entry into mitosis at the G2/M transition.
* Their levels fall in mid-mitosis.
M-cyclins
the fourth class of cyclins called the
Blank helps govern the activities of the G1/S
cyclins, which control progression through Start in
late G1.
G1-cyclins
