THE CELL CYCLE & MITOSIS by INpifxJ5

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									THE CELL CYCLE
  & MITOSIS
               OBJECTIVES
Understand Phases of Cell Cycle:

  – Particularly: S Phase, mitosis, and cytokinesis

  – Know cellular events in each phase of mitosis
         THE CELL THEORY

• All organisms consist
  of cells and arise from
  preexisting cells
        THE BIG PICTURE

• You and all other multicellular species got
  here through cell division

  – Human fertilized egg divides… 65 trillion cells
Once an egg becomes fertilized,
cellular division begins (by way
of mitosis & cytokinesis).



                          Continues
                             until an
                          integrated
                         organism is
                           produced
 HOW ARE NEW CELLS MADE?
Meiosis:




Mitosis:
AN EARLY VIEW
OF MITOSIS
  Paired “threads”


Late 1800s, scientists
observed thread-like
structures in nuclei of cells
undergoing division
Term mitosis originated
from “mitos” which translates
to thread in Greek
                    MITOSIS
• Parent cell splits to form 2 identical “daughter”
  cells
             ‘Parent’ cell:
                • original cell within body


                Daughter cells:
                    • precise duplicates of parent cell
                     (including duplicate chromosomes)
                 MITOSIS
Occurs In All Eukaryotes:
  – Plants
     • Occurs primarily at tips of roots and shoots


  – Animals
     • Occurs in many cells in the body:
FUNCTIONS OF MITOSIS
Mitosis Allows:
• Growth &
  development

• Cell replacement
  (damage repair)

• Asexual reproduction
 AN OVERVIEW OF THE CELL CYCLE
                       Parent cell

      Process of
      DNA Synthesis                     DNA Synthesis
      And Cellular
      Division

                                            Mitosis &
                                            Cytokinesis

         Two daughter cells

Parent & daughter cells contain same complement of chromosomes.
     CHROMOSOMES
Chromosomes:
               T- A
               G -C
               C-G




                      Single chromatid:
                          • DNA double helix
                          • Protein
           CHROMOSOMES
• Chromosomes
  are composed of
  DNA and
  Histone Proteins
           CHROMOSOMES
Number of
chromosomes
per cell depends
on species:

  – Human
KARYOTYPES
DIFFERENCES IN DNA SEQUENCES ACCOUNT FOR VARIETY OF LIFE ON EARTH
          5´                  3´   5´                               3´        5´                   3´
               T          A         T                   A

               G          C             G C

               C          G                 C G
               T          A             A                   T

               T          A             A                       T
               C          G                     C                   G
               G          C                                 G

               A          T                                 A T
               T          A                         T               A

               C          G             C                       G

               T          A             T           A

               G          C

               T          A                 A       T
               G          C         C                   G

               T          A                 A                       T
          5´                  3´        5´                               3´        5´         3´
                Cartoon of                      Cartoon of                    Space-filling model of
               base pairing                     double helix                      double helix
Cell Division Requires:
• Replication:                    THE CELL CYCLE:
  – DNA & cellular organelles    The Cell’s Time Clock

• Division:
  – Nucleus & genetic material


  – Cytoplasm & cell membrane
              THE CELL CYCLE
Cell Cycle Consists of:

• Interphase:
  – Non dividing cell



• Mitosis & Cytokinesis:
  – Small portion of cell cycle
Interphase:
Three sub phases:
                    INTERPHASE
• G1

• S




• G2
Some cells do not go through the
cell cycle!
                                     THE CELL
                                      CYCLE

  – Do not undergo DNA replication
    or cellular division
DNA REPLICATION (“S” PHASE)
S Phase:
• DNA replication


  • Daughter cells receives same
    complement of chromosomes
    as parent
       MORE SPECIFICALLY….
DURING S PHASE:


• Each chromosome is used as a template to
  produce a new double helix
Single chromosome
(one chromatid)         Two double helices

         Protein that
         copies DNA


                                             Two sister
                                             chromatids




SINGLE                  Each double helix
DOUBLE                  has one original strand
HELIX
After S-phase:
• One chromosome consists of 2 sister chromatids
• Each chromatid is made of one original and one duplicate strand
                                                         of DNA




                                           centromere




                        2 sister chromatids
G Phases:
                         GAP
• Gap phases separate
                         PHASES
  mitosis from S Phase
      M/ C

             G1
 G2                        MITOSIS
       S

Mitosis:

• Involves separation of
  copied chromosomes
  into separate cells
     M/ C
                 MITOSIS
            G1
G2
                 • Mitotic stages categorized
      S            by what’s happening in cell


                 • Stages include:
                       • Prophase
                       • Metaphase
                       • Anaphase
                       • Telophase &
                         Cytokinesis
PHASES OF MITOSIS




1. Prophase:
            PHASES OF MITOSIS




                3. Anaphase:   4.   Telophase &
2. Metaphase:
                                    Cytokinesis:
CYTOKINESIS Cytokinesis:
         IN
            • “Cleavage” furrow forms
   ANIMALS     at cell equator until cell
                      splits in two
Cytokinesis:                 CYTOKINESIS
• In plants, cell wall
                             IN
  material forms plate b/w
  two cells
                             PLANTS
CANCER
Cancer:
                CANCER
Tumors:
• Abnormal growing mass of cells
• Two types:
   – Benign tumors



  – Malignant tumors
CANCER
                 CANCER
Treatments:
• Surgery



• Radiation



• Chemotherapy

								
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