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0:00
My name is Bela Novak, and I am
the professor of systems biology
at the University of Oxford in
the department of biochemistry.
I will talk about
the systems biology
of the eukaryotic
cell cycle control.
0:14
This slide shows a simple
cartoon of the cell cycle.
The cycle starts with
a cell in G1 phase
with unreplicated chromosomes.
Although eukaryotes have
more than one chromosome,
I only show one of them here
as a straight gray line.
Chromosomes are
replicated during S-phase
of the cycle, which
follows G1 in the cycle.
Replication creates two
identical sister chromatids,
which are held together
by cohesin complexes.
After another gap phase
called G2, the cell
enters into mitosis, which
is also called M-phase.
The goal of M-phase
is to separate the two
sister chromatids within the cell.
Successful separation of
sisters requires biorientation
of all chromosomes on the
bipolar's mitotic spindle
during prometaphase of mitosis.
Once biorientation is completed,
the cell enters into metaphase
and segregates the two sister
chromatids during anaphase.
Finally, the cell divides
into two daughter cells
and the process can
be repeated again
depending on the
external conditions.
1:24
Cell cycle progression is
characterized by transitions
that the cell decides to enter
into the next phase of the cycle.
The first decision is
in G1 phase and it's
called start or restriction
point that the cell
decides to proliferate
or stay quiescent.
The G1/S transition marks the
initiation of replication.
Entry into mitosis is controlled
by the G2/M transition.
Segregation of sister
chromatids is decided
before metaphase/anaphase
transition takes place.
The final decision is exit
from mitosis and to divide
into two daughter cells.
Before each cell cycle
transition, the cell
has to be sure that conditions
are right for the next step.
Therefore, each cell
cycle transition
is a decision-making process.
