Transcript Chapter 6 Section 2 Notes

Chapter 6 Section 2
Cell Cycle
The Life of a Eukaryotic Cell

The Cell Cycle
◦ The cell cycle is a
repeating sequence of
cellular growth and
division during the life of
an organism.
◦ A cell spends 90 percent
of its time in the first
three phases of the cycle,
which are collectively
known as the interphase.
The Cell Cycle

The five phases of
the cell cycle are:
◦ First growth (G1)
phase:
 Cell grows
rapidly
 Cell carries out
routine functions
The five phases of the cell cycle are:

Synthesis (S) phase:
◦ DNA is copied
The five phases of the cell cycle are:

Second growth
(G2) phase:
◦ Cell continues to
grow
◦ Cell prepares to
divide its nucleus
The five phases of the cell cycle are:

Mitosis
◦ Process that the
nucleus divides into
two nuclei.
The five phases of the cell cycle are:

Cytokinesis
◦ Process that
equally divides
the cytoplasm
◦ Pinches the
parent cell into
two new
daughter cells
Control of the Cell Cycle

The cell has key
checkpoints
(inspection points)
at which feedback
signals from the cell
can trigger the next
phase of the cell
cycle.
Control of the Cell Cycle

Other feedback
signals can delay the
next phase to allow
for completion of
the current phase
(yellow or red light).
Control of the Cell Cycle

Control occurs at three
principal checkpoints:
◦ Cell growth (G1) checkpoint:
 Is the cell too big?
 If yes, the cell will prepare
to divide
 If no, the cell will continue
to grow.
Control occurs at three principal
checkpoints:

DNA synthesis (G2)
checkpoint:
◦ Is the DNA properly
replicated:
 If yes, mitosis will occur.
 If no, DNA will
repaired.
Control occurs at three principal
checkpoints:

Mitosis checkpoint:
◦ Did the nucleus
properly divide?
 If yes, cytokinesis will
occur.
 If no, mitosis must be
completed.
When Control is Lost: Cancer

Certain genes contain
the information
necessary to make
the proteins that
regulate cell growth
and division.
When Control is Lost: Cancer
If one of these genes
is mutated, the
protein may not
function, and
regulation of cell
growth and division
can be disrupted.
 Cancer: the
uncontrolled growth
of cells.
