Transcript Mitosis

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Cellular Reproduction
Chapter 9
9.1: Cellular Growth
MAIN IDEA: Cells grow until they
reach their size limit, then they
either stop growing or divide.
Cell Size DON’T COPY
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Most cells – only 100 micrometers in
diameter
Why are they so small???
Do large or small cells perform tasks
more efficiently?
Surface Area : Volume DON’T
COPY
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This ratio is extremely important
to cells
To calculate for a cube:
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Surface area = ?
Volume = ?
Surface Area : Volume DON’T
COPY
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Surface Area of cube = L x W x 6
Volume = L x W x H
Calculate SA:V ratio
Surface Area : Volume DON’T
COPY
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What happened to the ratio when
the cells became larger?
Surface Area : Volume DON’T
COPY
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As cell grows, volume increases
faster than surface area, so this
ratio becomes smaller
LARGER ratio (smaller cells) –
more beneficial to cells
Cell needs large surface area to get
enough nutrients and expel wastes
efficiently
Cell’s Life Cycle
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Cells grow only so big; too big
makes cell inefficient
If cell reaches size limit it:
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Stops growing OR
Divides
When cells divide, they make an
exact duplicate of themselves.
Result = 2 identical cells
Eukaryotes’ Cell Cycle
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Cycle of cells growing and dividing
After 1 complete cycle, 1 cell
becomes 2 cells
3 main parts:
 Interphase
 Division (Mitosis)
 Cytokinesis
Interphase
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Cell spends most of its
life in interphase
Called “resting” phase,
but cell is chemically active
 Metabolism (chemical
reactions)
 Preparation for division
3 Parts of Interphase
Interphase
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G1:
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Cell grows, active metabolism,
organelles duplicated
S: DNA replicated
G2:
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Has twice as much DNA as G1 phase cell,
prepares for mitosis, triggers division and
ends interphase
Mitosis (M) Phase
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Mitosis – nucleus and nuclear material
divide
Chromosomes can be seen under
microscope
Divided into 4 sub-stages
Chromatin
Chromosomes
Cytokinesis
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Cytokinesis - when cytoplasm
divides
9.2: Mitosis and
Cytokinesis
MAIN IDEA: Eukaryotic cells
reproduce by mitosis, the process of
nuclear division, and cytokinesis, the
process of cytoplasm division.
Mitosis
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Nuclear division
Continuous process
Seen in stages
Result = 2 genetically identical
daughter cells
Stages of Mitosis
1.
2.
3.
4.
Prophase
Metaphase
Anaphase
Telophase
Prophase
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Pro = first
Chromatin coils, shortens, and thickens
into chromosomes
Nuclear membrane starts to disappear
Prophase
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Spindle fibers (microtubules) form
in cytoskeleton, and chromosomes’
centromeres attach to fibers
Spindle apparatus = all microtubule
fibers and centrioles (in animal cells)
Prophase
Metaphase
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Meta = change
Pairs of chromosomes move to center of
cell, along equator, perpendicular to
spindle fibers
Anaphase
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Ana = up
Chromatids separate, each pair moving to
opposite ends of cell along spindle fibers
Telophase
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Telo = end
Chromosomes reach opposite ends of the
cells; new nuclear membrane starts forming to
make 2 identical nuclei
Cytokinesis
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Cytoplasm divides in half, duplicated
organelles move apart
Plant and Animal Cells
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Similar process of mitosis, but some
differences
Animal cells have 2 centrioles
Plant cells form a cell plate during
cytokinesis (preliminary cell wall);
animal cells pinch across middle instead
to separate
Prokaryotes
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Binary fission
Chromosome replicates
Cell elongates
Membrane/wall forms in middle,
dividing cell
Name the phase
9.3: Cell Cycle
Regulation
MAIN IDEA: The normal cell
cycle is regulated by cyclin
proteins.
Normal Cell Cycle
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Timing and rate of cell cycle
controlled by 2 substances:
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Cyclins – proteins
Cyclin-dependent kinases (CDKs) –
enzymes that bind to cyclin
Different combinations signal
different activities during the cell
cycle
Activities Controlled by
CDK/Cyclin:
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Start of cell cycle
DNA replication
Protein synthesis
Nuclear division (mitosis)
End of cell cycle
Abnormal Cell Cycle: Cancer
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Cells divide repeatedly and uncontrollably
No ability to stop the progression of
division at checkpoints (which allow
normal cells to stop dividing if something
goes wrong)
Cancer cells overcrowd normal cells,
stopping their normal function and killing
the organism
Causes of Cancer
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Changes/mutations in DNA affect
proteins that control cell cycle
Carcinogens – substances or agents
that cause cancer
What are Some Common
Carcinogens?
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Tobacco
Exposure to x-ray radiation
Exposure to UV radiation (from Sun)
Air pollution
Alcohol
Food with many preservatives
Genetics
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Higher risk of mutations over time –
so more likely for older people to
develop cancer
Can run in families
Apoptosis
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Programmed cell death
Occurs in development – webbing
between fingers/toes
Occurs in plants losing leaves
Prevents damaged cells from dividing
Prevents cancer
Stem Cells
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Unspecialized cells – specialize under
right conditions
Embryonic – result shortly after
fertilization; cells eventually specialize
into tissues (controversial research)
Adult – always found in some tissues
Can be used to treat certain
diseases/conditions