The Cell Cycle

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The Cell Cycle

• PART 2
• Honors Genetics
• Ms. Gaynor

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The Cell Cycle

• The mitotic phase alternates with interphase in
  the cell cycle
• Interphase?mitosis?interphase?mitosis

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Phases of the Cell Cycle

• The cell cycle consists of
• The mitotic (M) phase
• Interphase (90 of the cells life)

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Interphase can be divided into subphases

• G1 phase (GAP 1 phase)
• cell grows in size
• varies most in length from cell to cell
• S phase (synthesis phase)
• DNA is copied (DNA replication)
• Single ? Double
• Other organelles are copied
• (ex centrosomes in animal cells)
• G2 phase (GAP 2 phase)
• More growth and preparation (make proteins) for
  mitosis
• http//www.cellsalive.com/cell_cycle.htm

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Another G phase of Interphase

• Called G0 phase called the resting phase
• The cell exits the cycle and (usually) does NOT
  reproduce again
• Ex muscle cells, nerve cells, red blood cells

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InterphaseIntermission or Inbetween

• not part of mitosis
• Includes stages G1, S, and G2 of the cell cycle
• DNA is in chromatin form
• Nucleus nucleolus present
• Longest phase of cell cycle

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The Mitotic (M) phase

• Is made up of 2 parts
• 1. Mitosis? division of the nucleus (called
  Karyokinesis)
• 2. Cytokinesis ? division of the cytoplasm

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Mitosis

• Continuous pathway (Early, Mid, Late)
• Consists of 4 phases and cytokinesis
• Prophase
• Metaphase
• Anaphase
• Telophase
• Cytokinesis

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Prophase (Xs)Pack Together

• Chromatin ? Chromosomes
• DNA packs together
• Mitotic spindle fibers form from centrosomes
• Centrioles are in centromsomes in animals
• appear as asters in animals
• Microtubule Organizing Centers (MTOCs) (in
  plants)
• Centrosomes Spindle fibers move towards poles
  
• Late Nucleus and nucleolus disappear
• kinetochore fibers attach to each kinetochore on
  each chromosome ? they begin to migrate toward
  the cell center

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Mitotic Spindle Fibers

• Two types of spindle fibers
• Kinetochore fibers
• Polar fibers

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Metaphase (Xs)Meet in the Middle

• Chromosomes line up in the middle of cell
• Called equatorial or metaphase plate
• Kinetochore spinder fibers pull and tug
  chromosomes to line up

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Anaphase (Vs)Adios and Away

• SISTER CHROMATIDS separate and begin moving to
  opposite ends (poles) of the cell
• Polar fibers lengthen and elongate the cell
• Late anaphase ? each pole contains a complete set
  of single chromosomes
• NOTE This is the only time there is DOUBLE the
  amount of DNA in ONE cell

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• In anaphase, sister chromatids separate
• And move along the kinetochore microtubules
  toward opposite ends of the cell

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Telophase (Vs)Two New Cells

• The spindle fibers dissappear
• Two daughter nuclei and nucleoli begin to form at
  the two poles
• Nuclear envelopes reforms from the fragments of
  the parent cells nuclear envelope and other
  portions of the endomembrane system
• Chromosomes ? chromatin

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CytokinesisDivision of the Cytoplasm

• Occurs in Late telophase
• In animal cells
• a cleavage furrow forms, which pinches the cell
  in two.
• In plant cells
• vesicles from the Golgi apparatus produce a cell
  plate at the middle of the cell
• At the end of cytokinesis, there are two distinct
  IDENTICAL daughter cells.

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Cytokinesis A Closer Look

• In animal cells
• Cytokinesis occurs by a process known as
  cleavage, forming a cleavage furrow

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• In plant cells, during cytokinesis
• A cell plate forms

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Mitosis in a plant cell
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Cell Cycle and Mitosis Animations

• http//www.ucopenaccess.org/courses/APBiologyI/cou
  rse20files/multimedia/lesson17/lessonp.html
• http//highered.mcgraw-hill.com/olcweb/cgi/pluginp
  op.cgi?itswf535535/sites/dl/free/0072437316
  /120073/bio14.swfMitosis20and20Cytokinesis
• http//www.sumanasinc.com/webcontent/animations/co
  ntent/mitosis.html
• http//www.johnkyrk.com/mitosis.html

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Remember

• IPMATc
• I peed on the mat, see.
• Lets do the Mitosis Hand Cheer!