mitosis
TRANSCRIPT
No Bellringer This Week
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Agenda• NOTES: Mitosis
– Details of Chromosome Structure– Organelles Involved in Division– Mnemonic Device for PMATC– Details of each step of Mitosis
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Structure of Chromosomes• Chromosomes are tightly packed bundles
of DNA that look like the letter X.• The left and right halves of chromosomes
are identical strands called “Sister Chromatids”.
• The spot where the chromatids connect together is called the centromere.
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ChromosomChromosomeses
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Nuclear Membrane• The Nuclear Membrane is the outer skin
of the nucleus.• It is the the “Sac” that holds Chromatin.• It is sometimes called the Nuclear
Envelope.
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Cytoskeleton• The cytoskeleton is a network of protein
fibers that run throughout the cell.• These fibers maintain the shape of a cell
and act as tiny muscles to stretch and move.
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BLUE = MicrotubulesGREEN = Intermediate FilamentsRED = Microfilaments
Mitotic Spindle• The mitotic spindle is a collection of fibers
that pull chromosomes apart during mitosis.
• It has 3 major components– Centrioles: A pair of organelles that anchor the
mitotic spindle at opposite ends of the cell.– Asters: Short fibers that radiate out from the
centrioles in order to hold their position– Kinetechore fibers: Long fibers that pull
chromosomes apart and toward either end of cell.
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Steps of Mitosis• Mitosis is the division of Eukaryotic
Cells.• It has 5 steps
– Prophase– Metaphase– Anaphase– Telophase– Cytokinesis
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Pass Me Another Tasty Cupcake
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Pimps Make All That Cash
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Pet My Alligator, Tom Cruise
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P.M.A.T.C.
• Pass Me Another Tasty Cupcake
• Pimps Make All That Cash
• Pet My Alligator, Tom Cruise
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Prophase• Chromatin in the DNA coils to make
chromosomes• The nuclear membrane breaks down,
releasing chromosomes into the cytoplasm
• Centrioles move to opposite ends of the cell and the mitotic spindle forms between them.
• Kinetechore fibers from each half of the spindle attach to the centromere region of each chromosome.
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Metaphase• Kinetechore fibers of the spindle move
chromosomes towards center of the cell.
• By the end of this phase all chromosomes are lined up along the “equator”.
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MetaphaseMetaphase
ChromosoChromosomes lined mes lined at the at the EquatorEquator
Asters at Asters at the polesthe poles
Spindle Spindle FibersFibers
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Anaphase• Chromosomes are split apart and Sister
chromatids are pulled in opposite directions
• This occurs very quickly (Less than 5 minutes)
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AnaphaseAnaphase
Sister Sister ChromatidChromatid
s being s being separatedseparated
Telophase• Sister chromatids arrive at opposite ends
of the cell and begin converting back into chromatin.
• A nuclear envelope forms around each set of DNA to create new nuclei.
• The mitotic spindle is broken down.
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Cytokinesis• The Cell Membrane pinches together
between the 2 newly formed nuclei• This movement is done by the
cytoskeleton.
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BrainPOP: Mitosis
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Assignment• 17 review questions• Due Tomorrow
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