Download Cell Cycle Regulation

Cell Cycle Regulation
The normal cell cycle is regulated by
cyclin proteins.
Normal Cell Cycle
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The timing and rate of cell division
are important to the health of an
organism.
The rate varies depending on the
type of cell.
So what makes it happen?
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Mechanisms involving proteins and
enzymes controls the cell cycle.
Normal Cell Cycle
The role of Cyclins
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What is all involved in the starting of a
car?
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Twisting of the key
A signal is sent to the ignition
Then a signal is sent to the engine to finally
start.
Cell Cycle is Driven:
 Similarly,
the cell cycle in
Eukaryotic cells is driven by a
combination of two substances
that signal cell reproduction
processes.
Proteins called CYCLINS bind to
 Enzymes called cyclin-dependent
kinases (CDK)
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Cyclins and CDK’s
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When binded together during
interphase and mitosis they control
the processes of the cell cycle.
There are different combinations
that control different stages.
Cyclins and CDK in the Cell Cycle
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G1 stage of interphase: CDK and Cyclin
bind to start the cell cycle.
Other combinations
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Replicate DNA
Protein synthesis
Nuclear divisions
Built in Checkpoints
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The cell has built in checkpoints
that if everything is not perfect,
then it will stop the cycle.
Example: In G1 there is a
checkpoint that monitors for DNA
damage.
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There are checkpoints in S,G1, and
throughout mitosis:
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Spindle fiber checkpoints
Cyclin and CDK’s
So What happens if an abnormal cell
divides and repeats cycle.
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Can you think of an example of
abnormal cells?
Cancer Cells
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Even though it seems
like a fool proof
system there can be
some mistakes.
Cancer is the result
when cells do not
respond with the
normal cell cycle.
Cancer:

The uncontrolled
growth and division
of cells
Compare Times
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Normal:
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Interphase:
120min
Prophase: 60min
Metaphase: 10min
Anaphase: 3min
Telophase: 12min
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Cancerous:
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Interphase: 16min
Prophase: 15min
Metaphase: 2min
Anaphase: 1min
Telophase: 3min
Hypothesize what would happen to the
chicken stomach normal cells if the
cancerous cells continued to reproduce
Cancer Cell Growth
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Cancer cells crowd out healthy cells
by a high reproduction rate.
Check out times for normal chicken
stomach cells and Cancerous
stomach cells.
The cancerous cells spend little time
in interphase which means they fly
through the process of division and
will continue as long as they have
the nutrients they need.
How Cancer Cells get into Your Body
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Cancer cells are a result of a
mutation of DNA in a cell.
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This makes changes in proteins that
effect the cell cycle.
Can also be due to various
environmental factors

Known as carcinogens: cancer causing
agents.
Questions for You:
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What can be done to get rid of
cancer?
Is it inheritable?
What can you do to decrease your
risk?
Cancer
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Cancer, which currently
claims the lives of 1 out
of every 5 people in the
United States & other
developed nations is a
disease of the cell cycle.
Cancer cells do not have
a properly functioning
cell cycle control system;
They divide excessively &
can invade other tissues
of the body.
This excessive growth
can result in an abnormal
mass of cells called a
tumor.
Terms related to Cancer
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Tumor – abnormal mass of cells
Benign tumor – an abnormal mass of essentially
normal cells always remain at their original site.
Malignant tumor – a mass of cancer cells which are
capable of spreading into neighboring tissues &
often to other parts of the body.
Metastasis – the spread of cancer cells beyond their
original site.
Carcinomas – Cancers which originate in the
external or internal coverings of the body, such as
skin or the lining of the intestine.
Sarcomas – cancers which arise in tissues that
support the body, such as bone & muscle
Leukemias & Lymphomas – cancers of blood forming
tissues, such as bone marrow, spleen & lymph
nodes.
Cancer Cells Differ from Normal
Cells
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Cancer cells are largely
unrestrained by the system
that normally controls cell
division.
They are not usually
affected by densitydependent inhibition.
They continue to divide
even in high densities.
Many cancer cells have cell
cycle control systems that
proceed past checkpoints
even in the absense of
growth factors.
Cancer cells have reduced
need for anchorage & often
grow without be attached to
a surface.
Treatment for Cancer
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Chemotherapy
Radiation
Both attempt to
halt the spread of
cancer by
stopping them
from dividing.
What we know…..
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We have learned that cells have
checkpoints that make sure cells have no
abnormalities before division.
Yet, we know that cancer is a result from
a mutation in DNA and the cell continues
to divide with out recognition of cell
mutation.
So there have been mistakes in cell
division that still allow the cell to live
and divide.
Although some cells are programmed
to death.
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Called Apoptosis:
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Programmed cell death
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Usually by shrinking or shriveling
Example:
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Development of your hand and foot.
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We all start out with webbed feet and
hands.
Cells die between our fingers and our
toes
Creating our separate fingers and toes
Stem Cells:
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Most Cells have specific processes
and jobs are known as “specialized”
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Example: Muscle, skin, and nerve
Although there was a discovery in
1998 finding there is one cell that is
unspecialized but, can be
specialized under certain
conditions=
 Stem
Cells
Stem Cells become a variety of Tissue
2 Types of Stem Cells
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Embryonic Stem Cells
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Adult Stem Cells
Embryonic
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After fertilization of
egg by sperm the cells
reproduce until
around 100-150 cells
These Cells are
unspecialized at this
point and known as
Embryonic.
These cells all
undergo certain
conditions that make
them specialized.
Adult Stem Cells
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Found in tissues
throughout the
body
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May be used to
repair tissue
Newborns even
have adult stem
cells
Controversy