If cancer is uncontrolled
cell division…why would
a cell divide in the first
place?
Brainstorm a list of reasons a
cell would divide.
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DNA “overload”
Trouble exchanging materials
Repair an injury
Replace old worn out cells
Asexual reproduction
Organism = growth
Why would a cell divide?
The Cell Cycle
The series of events that
cells go through as they
grow and divide.
http://wise.berkeley.edu
/webapp/teacher/index.
html
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Most cells are able to divide…
But some cannot, like:
Most nerve cells
 Brain cells
 Heart cells
 Blood cells
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Where does cell division occur?
Cut out your cells and
place them in
chronological order.
Glue them in your notebook once
you have approval.
What is the end product of
mitosis?
Steps of the cell cycle
Stop and
think: why
would it be
important to
do this each
time?
Step One: copy the DNA
Step Two: Split the DNA equally
between the 2 cells
Step three: Split the cell’s
contents
Life Cycle of a Cell
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Before a growing
cell becomes too
large it divides
The division results
in two essentially
identical cells called
“daughter cells”.
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Prior to division the
cell replicates all of
its DNA.
Replication solves
the problem of
information storage,
each daughter cell
receives its own
genetic information
Why would it be important that the cell copies
itself before dividing???
What would happen if a cell split into two without
copying itself? Would both sides survive?
Phases of Mitosis
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Interphase
In interphase the DNA
in the nucleus is in a
loose stringy form
called chromatin
DNA replication takes
place, copying itself to
get ready for mitosis
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During prophase
chromosomes
become visible,
centrioles take
position on opposite
sides of the nucleus
Nucleus disappears
and the nuclear
envelope breaks
down
Prophase
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Metaphase
Chromosomes begin
to line up across the
center of the cell
Each chromosome
is now connected to
a spindle fiber at its
centromere
The centromeres that join the sister
chromotids separate creating two
individual chromosomes
 Chromosomes continue to move until the
have separated into two groups near the
poles of the spindle
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Anaphase
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The chromosomes
gather at opposite
ends of the cell
Chromosomes begin
to lose their distinct
shape
Two new nuclear
membranes form
Telophase
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Cytokinesis
Cytokinesis is the
division of the
cytoplasm
Occurs at same
time as telophase
(not a different step
in mitosis)
Done a little
different in plant
and animal cells
Prophase Metaphase Anaphase Telophase