MITOSIS & CYTOKINESIS by Luk39cn2

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									MITOSIS & CYTOKINESIS
•   MITOSIS: The nucleus of a cell is divided into 2 nuclei with
    the same number & kinds of chromosomes as parent cell.
•   CYTOKINESIS: The division of the cytoplasm into 2 distinct
    cells.
•   CHROMOSOMES: Contain the genetic information (DNA) passed
    on to each generation. They differ in number with ea. Specie.
•   COMPOSITION OF CHROMATIN: Makes up chromosomes.
•     Condenses between cell division, chromosomes become visible.
•     Made up of DNA and proteins. The proteins fold the DNA to
    fit into the nucleus. DNA is 10,000 X the length of chromo.
•     Don & Ada Olins and Christopher Woodcock discovered that
    DNA was coiled around histone proteins.
•     Nucleosomes: Bead-like structures of DNA and histones
•    These are tightly compacted so they can separate in mitosis.
              CHROMOSOMES
•   CHROMOSOME STRUCTURE
•     Chromotids: Identical parts contained in chromosomes (2)
•     Centromere: Located near the center of chromatids (usually)
•   CELL CYCLE
•     A cell grows, prepares for division, and divides to form 2 new
    daughter cells.
•      Mitosis (M phase) Active cell division, nucleus into 2 new ones
•      Interphase (G1,G2,& S) Period of non cell division, where
    other life processes are carried out
•     Cytokinesis Where the cytoplasm and contents divide
•   See fig. 8-10
•     Cells go through the cycle in different rates: muscles vs. skin
          INTERPHASE
•   http://www.micro.magnet.fsu.edu/micro/gallery.html
•   INTERPHASE: The period between cell division
•      G1 (Gap 1): Cellular growth and development takes place
•      S: (DNA Synthesis): DNA replication takes place,
    synthesizing of proteins
•      G2 (Gap 2): Synthesis of organelles and materials required
    for cell division. Shortest of the phases.
•   Although this phase seems quiet a lot is going on:
•      synthesizing of mRNA
•      making of proteins
•      DNA is copied
•      ATP is made and utilized
•      specialized cells do most of their work: secretion, movement
    INTERPHASE
•
    PROPHASE
•
                PROPHASE
•   Longest of the phases taking between 50-60% of total time.
•   Chromosomes become visible because of coiling of chromotin
•   Centrioles separate and go to opposite sides of the cell
•      Centrioles contain tubulin, a microtubule protein
•   Chromosomes attach to fibers (spindles) near the centromere.
•     Spindles help move the chromosomes apart and are developed
    from the centrioles.
•   Centrioles are composed of microtubules.
•   Plant cells do not contain centrioles.
•   Near the end of the phase coiling becomes tighter, the
    nucleolus disappears, and the nuclear envelope breaks down.
         METAPHASE
• The shortest of the phases lasting only a few
  minutes.
• Chromosomes line up across the center (equator)
  of the cell.
• Microtubules connect the centromere of each
  chromosome to the poles of the spindle.
• Because of their starlike arrangement around
  the poles of the spindle, these microtubules are
  called ASTERS.
               ANAPHASE
•   Begins when the centromeres that joins the sister chromotids
    split.
•   As they separate the spindle grows longer.
•   The chromosomes move until they have separated into two
    groups near the poles of the spindles.
•   Anaphase ends when the movement of the chromosomes stops.
•   Force that separates the chromosomes isn’t known.
•      Microtubule cross-bridging
•      Microtubule assembly/disassembly
•      Actinmediated force generation
•          All have been proposed. Problem is that such a small
    force is needed to move a chromosome that pinpointing the
    cause is a problem.
    ANAPHASE
•
    TELEPHASE & CYTOKINESIS
•   Final stage of mitosis
•   Chromosomes uncoil into a tangle of chromatin in the regions
    where the nuclei of the daughter cells will form.
•   The nuclear envelope reforms around the chromatin.
•   Spindles break apart and nucleolus becomes visible.
•   We now have two nuclei w/ a duplicate set of chromosomes
• CYTOKINESIS
•   Division of the cytoplasm into two individual cells
•   Takes place in a number of ways:
•      In animal cells the cell membrane moves inward until the
    cytoplasm in pinched into two parts w/ their own nucleus etc.
•      In plants, a cell plate forms midway between the divided
    nuclei. It develops into a separate membrane w/ a cell wall.
TELOPHASE
    •
CYTOKINESIS
    •

								
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