Transcript chromosomes - Humble ISD

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
SHOWS: Cell division
genes can be turned on
and off
CELL DIVISION GENES
EXAMPLE: Cell division genes can be
turned on 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
Mitotic spindle
______________to
form in
NON-dividing
_______________
cells
Pearson Education Inc; Publishing as Pearson Prentice Hall
CELL CYCLE REGULATORS
Levels of this protein rose and fell with
the cell cycle so it was named
__________
CYCLIN because it seemed to
control the cell cycle.
A whole family of
CYCLINS have since been
discovered that regulate the
TIMING of CELL CYCLE
_____________________
in EUKARYOTIC CELLS
Pearson Education Inc; Publishing as Pearson Prentice Hall
OTHER REGULATORS
INTERNAL
______________
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
EXTERNAL
______________
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.
Pearson Education Inc; Publishing as Pearson Prentice Hall
Cancer cells have lost control
of their cell division genes
SEM Image by: Riedell
CHO (Chinese Hamster Ovary) cells in culture
NO CONTACT INHIBITION
Cancer cells don’t stop
when they touch nearby
cells. . .
they just keep growing!
See a video
That’s what makes
a tumor.
http://www.exn.ca/news/images/2000/08/02/20000802-cancer.jpg
Cancer cells
• Don’t stop dividing
• Like a “car with no brakes”
• Can spread to new places
(METASTASIS)
• ______________
Carcinogens are substances that
can damage DNA and cause cancer
Ex: Cigarette smoke (OR CHEW),
Radiation, chemicals in environment,
even viruses,
http://www.dfci.harvard.edu/abo/news/publications/pop/fall-winter-2004/images/metastasis_1.jpg
Cancer cells
Cancer is complicated and can have many
causes, but all cancers have one thing in
common . . .…
They have lost control over their
_____________.
CELL CYCLE
Many cancers cells have a damaged or defective
gene called p53
_____, so they can’t respond to
normal cell signals to control their growth.
UNCONTROLLED CELL GROWTH
• Cancer-disorder in which some of the
body’s own cells lose the ability to control
growth
– Cancer cell do not respond to the signals that
regulate the growth of most cells, the divide
uncontrollably and form masses of cell called
tumors that can damage, surrounding tissue
• Two types of tumors
– Benign-Does not spread to surrounding tissue (non-cancerous)
– Malignant-spreads and destroys healthy tissue (cancerous)
CANCER CONTINUED
• Causes
– Biological Agent-Viruses
– Chemical Agent-Carcinogens-tobacco
– Physical Agent-radiation
*Treatments
* Surgery
* Radiation
* Chemotherapy-aimed at fast growing cells
How Cancer Begins
Page 12
• Changes in genes that influence the cell
cycle can cause the transformation of a
normal cell into a cancer cell.
• Two types of these genes
– The first type codes for proteins that stimulate
cell division; these are usually turned-off in nondividing cells
– They become ONCOGENES (cancer gene) by
mutation
– A common oncogene, ras, is present in mutated
Page 12 Continued
• The second type of gene associated with
cancer is a TUMOR SUPPRESSOR GENE
– These code for proteins that normally restrain
cell division
– In cancer tumor suppressor genes have been
inactivated by mutation
– An inherited mutation in one copy of a tumor
suppressor gene results in higher risk of cancer
Page 12 Continued
• Almost 50% of human cancers are
associated with a mutation in the tumor
suppressor gene p53
• P53 protein normally acts as an emergency
brake in the cell cycle, but when mutated
does not prevent unchecked cell division
• Cancers include breast, colon, lung, prostate,
and skin
Surviving Cancer
Page 13
• In the United States, about one of every five
deaths-more than half a million each yearare caused by cancer. (Only heart disease
kills more)
– Lung cancer is the number one cancer killer
– Colorectal, breast and prostate are the next
most common
– Cancer survival is measured by the
percentage of cancer patients who survive a
Page 13 Continued
• Cancer survival is influenced by the type of
cancer and by the stage at which a cancer is
diagnosed
• Cancers range from Stage 1, early onset of
cancer to Stage 4, the most advanced cancer
• EX: Colorectal cancer Stage 1, 5-yr survival
rate is 96%; Stage 4 colorectal cancer 5-yr
survival rate is 5%
• Pancreas cancer 5-yr rate is only 4%
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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)
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;
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;