CHROMOSOMES

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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.
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REGULATING the CELL CYCLE

• http//www.travel-net.com/andrews/images/animatio
  ns/traffic.gif

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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.
SHOWS Cell division genes can be turned on and
off
Cells grow until they touch other cells
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• CELL DIVISION GENES

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.
turned on
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• 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 dont divide once they
form (nerve cells)
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• CELL CYCLE REGULATORS

In early 1980s scientists discovered aprotein
in dividing cells that caused a ______________to
form in _______________ cells
Mitotic spindle
NON-dividing
Pearson Education Inc Publishing as Pearson
Prentice Hall
7

• CELL CYCLE REGULATORS

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
CYCLIN
TIMING of CELL CYCLE
Pearson Education Inc Publishing as Pearson
Prentice Hall
8

• OTHER REGULATORS

INTERNAL
______________ REGULATORSProteins that respond
to events inside the cell. Allow cell cycle to
proceed only if certain processes have
happened EX Cell cant enter mitosis until all
the chromosomes have been copied
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• OTHER REGULATORS

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
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il_HumanTail.gif
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• EXTERNAL REGULATORS

Molecules on the surface of neighboring cells act
as signals to slow down or stop the cells
cycle. These signals prevent excessive growth
and keep tissues from disrupting each other.

Pearson Education Inc Publishing as Pearson
Prentice Hall
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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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• NO CONTACT INHIBITION

Cancer cells dont stop when they touch
nearby cells. . . they just keep
growing! Thats what makes a tumor.
See a video

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

• Dont 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
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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 cant respond to
• normal cell signals to control their growth.

CELL CYCLE
p53
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ANTI-SMOKING commercial
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(No Transcript)
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SOUTH DAKOTA CORE SCIENCE STANDARDS
LIFE SCIENCEIndicator 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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Core High School Life SciencePerformance
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
High school students performing at the PROFICIENT level describe the relationship between structure and function compare and contrast the cell cycles in somatic and germ cells
High school students performing at the BASIC level recognize that different structures perform different functions describe the life cycle of somatic cells