The Cell Cycle and Mitosis

							          10-2
The Cell Cycle and Mitosis
10-2 The Cell Cycle and Mitosis
  The Cell Cycle
      biologists originally considered the
       period between cell division called
       interphase as a “resting” period
          we now know there is a great deal of cell
           activity occurring during interphase
          cell cycle : the period of time from the
           beginning of one cell division to the
           beginning of the next
Interphase
   G1, S and G2 make up interphase
       Time when a cell is not dividing
       The cell is preparing to divide
            The four phases of
              the Cell Cycle
1.   G1 phase
        period of growth while synthesizing proteins and
         organelles; high metabolism
2.   S phase
        synthesis of DNA and duplication of chromosome
3.   G2 phase
        shortest of 3 phases
        organelles and molecules required for cell division are
         produced; metabolism
4.   M phase
        cell division: mitosis and cytokinesis
G0: when a cell exits the cycle
   Some cells stop dividing
   This is called G0
   Many cells never divide again like our
    nerve and muscle cell
   Some cells can re-enter the cycle and
    divide…like some of our liver cells
         3%
21%          M

                            G1
        G2            42%
                 G1         S
                            G2
         S
                            M


  34%
               G1 phase




M phase

                          S phase


          G2 phase
     Mitosis
        Divisions of The Cell Cycle
        Divided into four phases
1.       Prophase
          The first and longest phase when the
           chromosomes become visible
             Become shorter and thicker
          Centrioles : two tiny structures located in
           cytoplasm near nuclear envelope. They
           move to opposite ends of nucleus (not
           found in plant cells)
         Mitosis

         near the end of prophase, the nuclear
          envelope disintegrates, the nucleolus
          disappears, and chromosomes tightly coil
2.       Metaphase
         chromosomes line up along center of cell
         Spindles attach to the centromere
          Mitosis
3.       Anaphase
         centromeres split and sister chromatids separate
         chromosomes dragged by spindle fibers to poles
4.       Telophase
         chromosomes begin to disappear
         nuclear envelope reforms
         nucleolus becomes visible
        Cytokinesis
   last step in the M phase
       division of the cytoplasm
       occurs at same time as telophase
       In an animal cell
          cleavage furrow forms and two cells pinch in


       In a plant cell
            cell plate forms between two new nuclei
            cell plate develops into new cell membrane and
             cell wall
                                     Spindle
                                     forming
Centrioles




              Nuclear    Chromatin   Centromere                         Centriole
                                                    Chromosomes
             envelope
                                                  (paired chromatids)
                   Interphase        Prophase               Spindle

              Cytokinesis                                  Centriole


                                        Individual            Metaphase
                        Telophase     chromosomes

  Nuclear                     Anaphase
 envelope
 reforming
Section 10-2


                                            Spindle
                                            forming
       Centrioles




                     Nuclear    Chromatin   Centromere                         Centriole
                                                           Chromosomes
                    envelope
                                                         (paired chromatids)
                          Interphase        Prophase               Spindle

                     Cytokinesis                                  Centriole


                                               Individual            Metaphase
                               Telophase     chromosomes

         Nuclear                     Anaphase
        envelope
        reforming
Section 10-2


                                            Spindle
                                            forming
       Centrioles




                     Nuclear    Chromatin   Centromere                         Centriole
                                                           Chromosomes
                    envelope
                                                         (paired chromatids)
                          Interphase        Prophase               Spindle

                     Cytokinesis                                  Centriole


                                               Individual            Metaphase
                               Telophase     chromosomes

         Nuclear                     Anaphase
        envelope
        reforming
Section 10-2


                                            Spindle
                                            forming
       Centrioles




                     Nuclear    Chromatin   Centromere                         Centriole
                                                           Chromosomes
                    envelope
                                                         (paired chromatids)
                          Interphase        Prophase               Spindle

                     Cytokinesis                                  Centriole


                                               Individual            Metaphase
                               Telophase     chromosomes

         Nuclear                     Anaphase
        envelope
        reforming
Section 10-2


                                             Spindle
                                             forming
       Centrioles




                     Nuclear     Chromatin   Centromere                         Centriole
                                                            Chromosomes
                    envelope
                                                          (paired chromatids)
                          Interphase         Prophase               Spindle

                     Cytokinesis                                   Centriole


                                                Individual            Metaphase
                               Telophase      chromosomes

         Nuclear                      Anaphase
        envelope
        reforming
                               Cleavage
                                Furrow
Section 10-2


                                            Spindle
                                            forming
       Centrioles




                     Nuclear    Chromatin   Centromere                         Centriole
                                                           Chromosomes
                    envelope
                                                         (paired chromatids)
                          Interphase        Prophase               Spindle

                     Cytokinesis                                  Centriole


                                               Individual            Metaphase
                               Telophase     chromosomes

         Nuclear                     Anaphase
        envelope
        reforming
           Review Concept Map
                                        Cell Cycle

                                          includes




             Interphase                                          M phase
                                                                 (Mitosis)



           is divided into                                    is divided into




G1 phase      S phase        G2 phase         Prophase   Metaphase       Anaphase   Telophase