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Interest Grabber Answers. Knowing When to Stop Suppose you had a paper cut on your finger. Although the cut may have bled and stung a little, after a few days, it will have disappeared, and your finger would be as good as new.

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Interest Grabber Answers

Knowing When to Stop

Suppose you had a paper cut on your finger. Although the cut may have bled and stung a little, after a few days, it will have disappeared, and your finger would be as good as new.

1. How do you think the body repairs an injury, such as a cut on a finger?

The cut is repaired by the production of new cells through cell division.

2. How long do you think this repair process continues?

Cell division continues until the cut is repaired.

3. What do you think causes the cells to stop the repair process?

Students will likely say that when the cut is filled in, there is no room for more cells to grow.

regulating the cell cycle
REGULATING the CELL CYCLE

http://www.travel-net.com/~andrews/images/animations/traffic.gif

control of cell division
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

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EXAMPLE: Cell division genes can be ________ in case of injury.

Cells near injury are

stimulated to divide

to heal and replacedamaged/missing cells

and shut off when the

repair has been made.

CELL DIVISION GENES

turned on

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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 DIVISION GENES

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In early 1980’s scientists discovered aprotein in dividing cells that caused a

______________to form in

_______________ cells

CELL CYCLE REGULATORS

Mitotic spindle

NON-dividing

Pearson Education Inc; Publishing as Pearson Prentice Hall

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Levels of this protein rose and fell with

the cell cycle so it was named

__________ because it seemed tocontrol the cell cycle.

A whole family ofCYCLINS have since beendiscovered that regulate the_____________________

in EUKARYOTIC CELLS

CELL CYCLE REGULATORS

CYCLIN

TIMING of CELL CYCLE

Pearson Education Inc; Publishing as Pearson Prentice Hall

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INTERNAL

______________ REGULATORSProteins 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

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EXTERNAL

______________ REGULATORSProteins 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 divideEspecially important duringwound healing and

embryo development

OTHER REGULATORS

http://www.suite101.com/files/topics/6234/files/tail_HumanTail.gif

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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.

EXTERNAL REGULATORS

Pearson Education Inc; Publishing as Pearson Prentice Hall

cancer cells have lost control of their cell division genes
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.

See a video

NO CONTACT INHIBITION

http://www.exn.ca/news/images/2000/08/02/20000802-cancer.jpg

cancer cells
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,

Carcinogens

http://www.dfci.harvard.edu/abo/news/publications/pop/fall-winter-2004/images/metastasis_1.jpg

cancer cells1
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.

CELL CYCLE

p53

south dakota core science standards
SOUTH DAKOTA CORE SCIENCE STANDARDS

LIFE SCIENCE:Indicator 1: Understand the fundamental structures,

functions, classifications, and mechanisms found

in living things

9-12.L.1.1. Students are able to relate cellular functions and processes to specialized structures within cells.

  • Cell life cycles (ANALYSIS)

Examples: somatic cells (mitosis)

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