Transcript Notes - local.brookings.k12.sd.us

REGULATING
the
CELL CYCLE
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Control of Cell Division
Section 10-3
If center cells are removed,
cells near the space will
start to grow again.
Cells grow until they
touch other cells
Go to
Section:
SHOWS: Cell division
genes can be turned on
and off
CELL DIVISION GENES
EXAMPLE: Cell division genes can be
_________ in case of injury.
Cells near injury are
stimulated to divide
to heal and replace
damaged/missing cells
and shut off when the
repair has been made.
CELL DIVISION GENES
Some cells divide frequently
(some human skin cells divide once/hour)
Some cells divide occasionally
(liver cells divide about once/year)
Some cells don’t divide once they form
(nerve cells)
CELL CYCLE REGULATORS
In early 1980’s scientists discovered a
protein in dividing cells that caused a
______________to form in
_______________ cells
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CELL CYCLE REGULATORS
Levels of this protein rose and fell with
the cell cycle so it was named
__________ because it seemed to
control the cell cycle.
A whole family of
CYCLINS have since been
discovered that regulate the
_____________________
in EUKARYOTIC CELLS
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OTHER REGULATORS
______________ REGULATORS
Proteins that respond to events inside
the cell.
Allow cell cycle to proceed only if
certain processes have happened
EX: Cell can’t enter mitosis until all the
chromosomes have been copied
OTHER REGULATORS
______________ REGULATORS
Proteins that respond to events outside
the cell.
Signals tell cell to speed up or slow
down the cell cycle
EX:
Growth factors stimulate cells to divide
Especially important during
wound healing and
embryo development
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EXTERNAL REGULATORS
Molecules on the surface of neighboring
cells act as signals to slow down
or stop the
cell’s cycle.
These signals prevent
excessive growth and
keep tissues from
disrupting each other.
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Cancer cells have lost control
of their cell division genes
SEM Image by: Riedell
CHO (Chinese Hamster Ovary) cells in culture
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Cancer cells don’t stop
when they touch nearby
cells. . .
they just keep growing!
That’s what makes
a tumor.
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Cancer cells
• Don’t stop dividing
• Like a “car with no brakes”
• Can spread to new places
(METASTASIS)
• ______________ are substances that
can damage DNA and cause cancer
Ex: Cigarette smoke (OR CHEW),
Radiation, chemicals in environment,
even viruses,
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Cancer cells
Cancer is complicated and can have many
causes, but all cancers have one thing in
common . . .…
They have lost control over their
_____________.
Many cancers cells have a damaged or defective
gene called _____, so they can’t respond to
normal cell signals to control their growth.
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