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The Cell Cycle and
Mitosis
Why Do Cells Divide?
Why Do Cells Divide
1.
Healing and Tissue Repair
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An average human looses 105 pounds of
dead skin cells in their life
Every second, millions of your body cells
are injured or die and must be replaced
Replacement of dead cells also occurs in
plants
Why Do Cells Divide
2. Growth
 All plants and animals begin life as a single
cell
 Only two ways for an organism to grow: 1)
single cell gets bigger; or 2) the single cell
divides into more cells
Why Do Cells Divide
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One of the most important jobs of a cell is
to exchange materials with its environment
(the body or outside world)
The cell needs to get food and nutrients in
and waste out
Why Do Cells Divide
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Why Don’t Cells Just Keep Getting Bigger?
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Eventually a cell will reach a size where it will not
be able to get enough exchange of materials to
sustain cell function
Why Do Cells Divide
3.
Perpetuate Life
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Important for unicellular (prokaryotes)
organisms like bacteria – creates 2 new
organisms
Why Do Cells Divide
3.
Perpetuate Life
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Also essential for reproduction of multicellular
organisms
The Cell Cycle
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The repeating cycle in the life of a cell
Interphase : when a cell is preparing for cell
division; this is the majority of the time
Cell division : the process of 1 cell dividing
into 2 cells
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Mitosis: division of the nucleus
Cytokinesis : division of the cytoplasm
Interphase
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First Growth Phase (G1)
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Synthesis Phase (S)
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Period of growth for a cell
Produces new proteins and organelles
Cell synthesizes entire copy of DNA
Second Growth Phase (G2) – shortest phase
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Cell produces organelles and structures for cell
division
Mitosis:
What is it basically?
 DNA copies (chromosomes) are separated & sorted
into two sides of the cell
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the cell then splits in two and part of each parent is
carried to the two new cells.
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each ‘daughter’ cell is identical to the parent cell
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results in cells such as internal organs, skin, bones,
blood, etc.
Mitosis animation:
http://www.youtube.com/watch?v=2WwIKdyBN_s&feature=related
Interphase occurs just before
Mitosis begins:
DNA is replicated
along with
organelles and
other cellular
components and
the cell prepares
for division.
http://www.bioweb.uncc.edu/1110Lab/notes/notes1/lab6.htm
Before Mitosis :
Interphase
Animal cell
Plant cell
Photographs from: http://www.bioweb.uncc.edu/biol1110/Stages.htm
st
1
step in Mitosis:
Prophase (preparation phase)
•the DNA recoils, and the
chromosomes condense
•the nuclear membrane
disappears
•mitotic spindles begin to
form.
http://www.bioweb.uncc.edu/1110Lab/notes/notes1/lab6.htm
Mitosis Prophase
Animal cell
Plant cell
Photographs from: http://www.bioweb.uncc.edu/biol1110/Stages.htm
2nd step in Mitosis:
Metaphase (organizational phase)
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spindle fibres attach
to the
chromosomes at
the centromere
chromosomes line
up the middle of the
cell
http://www.bioweb.uncc.edu/1110Lab/notes/notes1/lab6.htm
Mitosis Metaphase
Animal cell
Plant cell
Photographs from: http://www.bioweb.uncc.edu/biol1110/Stages.htm
3rd step in Mitosis:
Anaphase (separation phase)
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the chromosomes
split at the
centromere
the ‘sister
‘chromatids are
pulled by the
spindle fibers to
opposite poles of
the cell.
http://www.bioweb.uncc.edu/1110Lab/notes/notes1/lab6.htm
Mitosis Anaphase
Animal cell
Plant cell
Photographs from: http://www.bioweb.uncc.edu/biol1110/Stages.htm
4th step in Mitosis:
Telophase
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the chromosomes, the
cytoplasm and organelles
divide into 2 portions.
this diagram shows the end
of telophase.
http://www.bioweb.uncc.edu/1110Lab/notes/notes1/lab6.htm
Mitosis Telophase
Animal cell
Plant cell
Photographs from: http://www.bioweb.uncc.edu/biol1110/Stages.htm
After Mitosis:
Cytokinesis
Beginning of cytokinesis in a plant:
the actual splitting
of the daughter
cells into two
separate cells is
called cytokinesis
 occurs differently in
both plant and animal
cells.
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http://www.bioweb.uncc.edu/1110Lab/notes/notes1/lab6.htm
Beginning of cytokinesis in an animal:
MITOSIS
Mitosis
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http://www.youtube.com/watch?v=2WwIKdyBN_s&feature=related
http://www.youtube.com/watch?v=VlN7K1-9QB0
http://www.cellsalive.com/mitosis.htm
http://www.sci.sdsu.edu/multimedia/mitosis/mitosis_gif2.html
http://www.teachersdomain.org/resource/tdc02.sci.life.stru.dnadivide/
http://highered.mcgrawhill.com/sites/0072495855/student_view0/chapter2/animation__mitos
is_and_cytokinesis.html
The Cell Cycle
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Remember iPMATc
Interphase
Mitosis
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Prophase
Metaphase
Anaphase
Telophase
Cytokinesis
Homework
1.
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4.
Describe the events in the cell cycle.
Explain how mitosis ensures genetic
continuity.
How does mitosis make the growth and
repair of cells possible in an organism?
Get a textbook and describe each phase
of mitosis along with a picture (pg. 30-32)
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Also define cytokinesis and apoptosis