Download Using your notes, look at each cell below and

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Cell Cycle and Cancer
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Introduction
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Model 1 – The Cell Cycle
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Cell growth and division is a function that characterizes all
living organisms. Looking at your own body, you can identify
numerous examples of cell division occurring at this very moment!
For example:
 Cell division of skin cells to replace those that have died and fallen off.
 Cell division in bone marrow to make red blood cells.
 Cell division of stomach cells to replace those that have been damaged due to exposure to the
hydrochloric acid released into the stomach.
These are just a few examples of the cell cycle in action. The cell cycle is a sequence of events that involve
growth and division. The cell cycle is organized into two major parts; interphase and mitosis. Interphase is
comprised of Gap1, DNA synthesis and Gap 2. When the cell is in interphase, it carries out normal
metabolic activity, grows, and replicates its’ DNA so that both daughter cells have a copy of it. Mitosis
follows interphase and is when the nucleus divides into two daughter nuclei. Following Mitosis the
cytoplasm splits and the cell divides into two identical daughter cells in a process called Cytokinesis.
Eukaryotic Cell Division
1. Which type of cell, prokaryotic or eukaryotic, does Model 1 apply to?
2. What stage(s) in the diagram
represent growth phase(s) for the cell?
3. During which stage of the cell cycle is
the genetic material duplicated?
4. Why must genetic material be
duplicated (also known as replication or
copying)?
5. What happens inside the cell
during Mitosis (M)? (If you start with
one nucleus, what do you end with?)
6. Which part of the process of cell division is not listed on the chart above? What happens during this
process?
Model 2: Mitosis
During the Cell Cycle the majority of the time is spent in interphase (up to 90%). Mitosis follows Interphase
and is defined as the process of producing two identical daughter cells from one parent cell. Mitosis follows
a series of steps called the mitotic process. Those steps in order are Prophase, Metaphase, Anaphase
and Telophase.
Using your notes, look at each cell below and decide which stage of the Cell Cycle it is in. Your options are
Interphase, Prophase, Metaphase, Anaphase and Telophase.
Plant Cells in Mitosis
Label the cells below:
1.
7.
13.
2.
8.
14.
3.
9.
15.
4.
10.
16.
5.
11.
17.
6.
12
18.
19. Count the number of cell’s that are in each phase and list the numbers below (make sure to label which
phase).
Prophase – During Prophase the chromatin
condenses down to chromosomes. Also, the
nuclear membrane and nucleolus disappear.
Finally the centrosomes move apart from each
other the spindle begins to form.
Metaphase - During metaphase the chromosomes
line up in the middle of the cell along the equator.
The spindle attaches to the chromosomes at a
spot called the centromere which is the middle of
the chromosome.
Anaphase – During Anaphase the chromosomes
are pulled apart by the spindle. Each chromosome
is made of two sister chromatids that are
identical. In Anaphase the sister chromatids are
split apart and move to opposite sides of the cell.
Telophase – During Telophase
the chromosomes are completely
separated. The nuclear
membrane and nucleolus reform
and you are left with two nuclei.
Mitosis is now complete.
Stages of Mitosis
Match each statement with the correct phase of mitosis or with the process of cytokinesis.
A. Prophase
B. Metaphase
C. Anaphase
D. Telophase
E. Cytokinesis
_______1. The phase during which the nuclear membrane reappears.
_______2. The phase during which the spindle attaches to the centromere of each sister chromatid
_______3. Cromatin (which is loose and thin) condenses down to solid chromosomes during this phase.
_______4. The nuclear membrane disappears before this phase starts.
_______5. During this phase the sister chromatids are separated and pulled away from each other
_______6. During this phase the cell pinches together and splits the cytoplasm.
_______7. Finally we see the beginning of two nuclei during this phase.
_______8. During this phase all the chromosomes are lined up together in the middle of the cell.
9. The events of the cell cycle are coordinated by various proteins in the cell. These proteins are encoded
by genes that are switched on and off in a highly controlled fashion. This ensures that the proteins required
for G1 are only produced during G1 and that the proteins required for mitosis are only produced during
mitosis. This allows multicellular organisms to precisely control when and where the cells in its body divide.
Indiscriminant, constant cell division does not allow multicellular organisms to maintain specific form and
functions of its tissues.
Make a prediction as to what would occur if the genes for proteins that control when and where cells of your
body divide were mutated (damaged)? Explain your thoughts.
Model 3: Regulation of the Cell Cycle
For many years, it was a mystery to scientists how cells controlled their cell division. Scientists now know
that the cell cycle is highly regulated by checkpoints that control cell growth and division. These checkpoints
can stop the cell cycle and prevent it from dividing when it would be harmful to the organism. When the
chemical signals controlling this process fail, very bad things start happening.
Part 1 Oncogenes: The bad guys, turn abnormal cell growth on (go/gas pedal)
An oncogene is a gene that has been mutated in a way that leads to signals that cause uncontrolled growth- i.e.,
cancer. This is like pushing down on a car’s gas pedal- you now have a gene that is telling the cell to "go, go, go!” and
never stop.
Part 2 Tumor suppressor genes: The good guys gone bad
Tumor suppressor genes in normal cells act as braking signals during phase G1 of the cell cycle, to stop or slow the
cell cycle before S phase. If tumor-suppressor genes are mutated, the normal brake mechanism will be disabled,
resulting in uncontrolled growth, i.e. cancer.
Oncogenes are mutated genes whose
PRESENCE can stimulate the
development of cancer.
Tumor suppressor genes are normal
genes whose ABSENCE can lead to
cancer.
7. What are two types of genes that play a major role in regulating the cell cycle? Describe what effect the
genes have on the regulation.
8. What would happen to a cell that experiences a mutation in a tumor-suppressor gene?
What is Cancer?
How does a cell “know” when it is time to divide? What controls these events to ensure that the division
occurs properly and correctly? These are critical questions to scientists who study the cell cycle because
not only do their answers provide insight into normal cell function, their answers help us better understand
diseases that arise when the process goes awry.
Figure A
Figure B
Normal Cells
Have external growth factors to divide
Contact inhibition – contact with other cells results
in stop of cell division
Age and die then replaced in controlled and
orderly manner with limited number of divisions
Cease to divide and die when there is DNA damage
or when cell division is abnormal
Cancer Cells
Lost need for positive growth factors
Continue to divide after contact
Unlimited number of cell divisions
Even with damage to DNA continue to divide even when large
amount of damage to DNA or when the cell is abnormal
10. Cancer cells do not stop dividing. Which picture above demonstrates abnormal cell division? Why?
11. Using the information in Model 3 Table, describe three differences between the cells pictured in the
diagrams A and B.