1. REGULATING the CELL CYCLE

2. 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)

3. What controls the cell cycle?
How does a cell know it’s time to divide?
What signals a G0 cell to return to cycle?
Where do signals come from?
What happens when cells
don’t respond to signals?

4. CELL CYCLE REGULATORS ______________ REGULATORS
Proteins that respond to events outside the cell.
Signals tell cell to speed/slow down cell cycle
EX: ______________________
stimulate cells to divide
important during wound healing
and embryo development

5. EXTERNAL SIGNALS ________ Cell division genes
in cells near injury TURN ON to heal and
replace damaged/missing cells
and TURN OFF when the
repair has been made.

6. Control of Cell Division
Cells receive signals from neighbors
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

7. 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.
Pearson Education Inc; Publishing as Pearson Prentice Hall

8. GROWTH FACTORS
___________________________________ Crowded cells stop dividing
______________________________ Cells must be attached in order to divide

9. OTHER REGULATORS ______________ REGULATORS
Proteins respond to events inside the cell.
Cell cycle proceeds only if certain processes have happened
EX: Cell can’t enter mitosis until all the
chromosomes have been copied

10. INTERNAL REGULATORS
In early 1980’s scientists discovered a protein in dividing cells that caused a
______________to form in
_______________ cells
Pearson Education Inc; Publishing as Pearson Prentice Hall

11. INTERNAL 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
Pearson Education Inc; Publishing as Pearson Prentice Hall

12. Slide from Kim Foglia

13. Slide from Kim Foglia

14. Protective ends on all chromosomes Protect DNA code from being lost
_____________
Protective ends on all chromosomes
Protect DNA code from being lost
Become shorter with each replication;
Older cells have shorter telomeres

15. Most cells divide 20-50 times in culture; then stop, age, die
HAYFLICK LIMIT-
Most cells divide times in culture; then stop, age, die
Dolly the cloned sheep died of “old age” at 6½
Cancer cells are “immortal”
HeLa cells from a tumor removed from a woman
(Henrietta Lacks) in 1951 are still reproducing in culture

16. Can you think of another kind of cell that
Telomerase = enzyme that lengthens telomeres
Cancer cells are “immortal”
have increased telomerase activity
Can you think of another kind of cell that
might have increased telomerase activity?
2009 Nobel Prize Physiology/Medicine
Discovery of Telomeres
Jack Szostak Carol Greider Elizabeth Blackburn.
VIDEO

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

18. 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
tumor suppressor gene called ____ .
Signals DNA repair enzymes
Holds cell at G1 checkpoint
Starts apoptosis of damaged cells

19. Slide from Kim Foglia http://www.explorebiology.com

21. NO CONTACT INHIBITION Cancer cells lose contact inhibition
They don’t stop dividing
when they touch nearby
cells. . .
they just keep growing!
That’s what makes
a tumor.

22. Slide from Kim Foglia http://www.explorebiology.com

23. CANCER CELLS Don’t respond to control signals Lose contact inhibition
Lose anchorage dependence
Telomerase enzymes maintain/replace telomeres
________________
process that changes
a normal cell into
a cancer cell

24. Cancer cells Don’t stop dividing Like a “car with no brakes”
_________________ Can spread to new places

25. Cancer cells
______________ are substances that can damage DNA and cause cancer Cigarette smoke (or chew), UV radiation, radiation, chemicals, pollution, genetics, viruses (HPV)
Vaccine can prevent cancer from HPV virus

26. Slide from Kim Foglia http://www.explorebiology.com

27. ANTI-SMOKING commercial

29. SOUTH DAKOTA CORE SCIENCE STANDARDS
LIFE SCIENCE: Indicator 1: Understand the fundamental structures,
functions, classifications, and mechanisms found
in living things
9-12.L Students are able to relate cellular functions and processes to specialized structures within cells.
Cell life cycles (ANALYSIS)
Examples: somatic cells (mitosis)

30. Core High School Life Science Performance Descriptors
High school students performing at the
ADVANCED level:
predict the function of a given structure;
predict the outcome of changes in the cell cycle;
PROFICIENT level:
describe the relationship between structure and function
compare and contrast the cell cycles in somatic and germ cells;
BASIC level
recognize that different structures perform different functions
describe the life cycle of somatic cells;