1. REGULATING the CELL CYCLE

2. Control of Cell Division
Section 10-3
If center cells are removed, cells near the space will start to grow again.
SHOWS: Cell division
genes can be turned on
and off
Cells grow until they touch other cells

3. 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.

4. 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)

5. 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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6. 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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7. 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

8. 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

9. 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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10. Cancer cells have lost control of their cell division genes
SEM Image by: Riedell
CHO (Chinese Hamster Ovary) cells in culture

11. NO CONTACT INHIBITION Cancer cells don’t stop when they touch nearby
they just keep growing!
That’s what makes
a tumor.

12. 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,

13. 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.

14. ANTI-SMOKING commercial