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The Cell Cycle and Cellular Reproduction

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					The Cell Cycle and Cellular
      Reproduction

         Chapter 9
                   Cell Cycle

 Cell Cycle – the orderly set of stages in life
  of cell between cell division and division of
  the daughter cells
 Can be separated into 2 phases:
     Interphase
     Mitosis




                    Mader; Biology, 9th Ed.
               Cell Cycle

Interphase
 Includes the normal functioning of the cell
 Represents the major part of the cell cycle
  in most normal cells
 Consists of 3 phases:
     G1
    S

     G2


                 Mader; Biology, 9th Ed.
Cell Cycle




 Mader; Biology, 9th Ed.
                   Interphase
G1 Stage
   Before DNA replication
   Protein synthesis
   Preparation for DNA replication
   Duplication of organelles
S stage
   S – DNA synthesis
   Duplication of chromosomes
G2 Stage
   Second gap phase
   Protein synthesis
   Prep for cell division (M Stage)
                      Mader; Biology, 9th Ed.
                     Mitosis
M Stage
   Mitosis
     Nuclear division
     Daughter chromosomes distributed to two
      daughter nuclei
   Cytokinesis
     Cell division
     Results in two genetically identical daughter
      cells

                     Mader; Biology, 9th Ed.
              Control of cell cycle
Cell cycle controlled by internal and external
signals
 External signals
       Growth factors
       Received at the plasma membrane
       Cause completion of cell cycle
   Internal signals
       Family of proteins called cyclins
       Increase and decrease as cell cycle continues
       Without them cycle stops at G1, M or G2
       Allows time for any damage to be repaired
                        Mader; Biology, 9th Ed.
Control of cell cycle




      Mader; Biology, 9th Ed.
                  Cell Cycle

 Essential part of cell life cycle cell death
 Cells die in 2 ways:
     Apoptosis
     Necrosis




                   Mader; Biology, 9th Ed.
                 Apoptosis

 Apoptosis – programmed cell death
 Necessary for normal growth and
  development of organism
     Development
     Damaged cells




                      Mader; Biology, 9th Ed.
                   Apoptosis

   Controlled by internal and external factor
     Ex. Mitochondrial damage
     Ex. Fas-Fas ligand interaction

   Caspase cascade




                    Mader; Biology, 9th Ed.
Apoptosis




 Mader; Biology, 9th Ed.
      Preparation for Mitosis

 DNA ordinarily exists within the nucleus as
  a tangled mass of chromatin
 DNA associated with histone proteins

 Prior to mitosis the DNA condenses into
  chromosomes
 Distinctly visible




                 Mader; Biology, 9th Ed.
Mader; Biology, 9th Ed.
                  Chromosomes

   Each species has
    a characteristic
    number of
    chromosomes
       Diploid (2n) - Two
        of each kind
       Haploid (1n) - One
        of each kind



                        Mader; Biology, 9th Ed.
              Chromosomes
                                             Two identical
                                              chromatids are called
                                              sister chromatids
                                             Attached to each
                                              other at centromere
                                                 During nuclear
                                                  division, sister
                                                  chromatids separate at
                                                  the centromeres, and
                                                  each duplicated
                                                  chromosome gives
                                                  rise to two daughter
Duplicated chromosome                             chromosomes
                    Mader; Biology, 9th Ed.
        Mitosis in Animal Cells
   Centrosome
     Outside of nucleus
     Microtubule organizing center

     Organizes mitotic spindle

     Bundle of microtubules

     Contains a pair of barrel-shaped organelles -
      centrioles
     Also contains an array of short microtubules -
      aster

                    Mader; Biology, 9th Ed.
             Mitosis in Animal Cells
   Prophase
       Chromatin has
        condensed
       Nucleolus disappears
       Nuclear envelope
        disintegrates
       Spindle begins to
        assemble
       Two centrosomes move
        away from each other
       Form microtubules in
        star-like arrays – asters
                            Mader; Biology, 9th Ed.
Mitosis in Animal Cells
                       Prometaphase
                             Kinetochores develop
                              on centromere of each
                              chromosome
                                    Specialized protein
                                     complex
                                    One over each sister
                                     chromatid
                                    Physically hook sister
                                     chromatids up with
                                     specialized microtubules
                                     (kinetochore fibers)
                                    These connect sisters
                                     to opposite poles of
                                     mother cell
       Mader; Biology, 9th Ed.
           Mitosis in Animal Cells
   Metaphase
       Chromosomes,
        attached to
        kinetochore fibers, are
        in alignment at center
        of cell – metaphase
        plate




                         Mader; Biology, 9th Ed.
Mitosis in Animal Cells
                       Anaphase
                             Centromere dissolves,
                              releasing sister
                              chromatids
                             Sister chromatids split,
                              producing daughter
                              chromosomes
                                    Daughter chromosomes
                                     are pulled to opposite
                                     poles


       Mader; Biology, 9th Ed.
             Mitosis in Animal Cells
   Telophase
       Spindle disappears as
        new nuclear
        envelopes form
        around the daughter
        chromosomes
            Chromosomes become
             diffuse chromatin again
            Nucleolus appears in
             each daughter nucleus



                             Mader; Biology, 9th Ed.
Mader; Biology, 9th Ed.
             Cytokinesis

 Cytokinesis accompanies mitosis in most
  cells, but not all
 Mitosis without cytokinesis results in a
  multinucleated cell
 Begins in anaphase, continues in
  telophase, but does not reach completion
  until the following interphase begins

                Mader; Biology, 9th Ed.
                   Cytokinesis
   Animal Cells
       Cleavage furrow, membrane indentation
        between daughter nuclei, begins as anaphase
        nears completion                    Deepens
                                                when a band
                                                of actin
                                                filaments
                                                (contractile
                                                ring) forms a
                                                circular
                                                constriction
                                                between the
                                                two daughter
                      Mader; Biology, 9th Ed.   cells
Animal Cell Division




      Mader; Biology, 9th Ed.
Mitosis/Cytokinesis in Plant Cell

   Meristematic plant tissue retains the ability
    to divide throughout the plant’s life
       Found at root and shoot tips




                      Mader; Biology, 9th Ed.
Phases of Mitosis in Plant Cells




            Mader; Biology, 9th Ed.
        Cytokinesis in Plant Cells

   Rigid cell wall surrounding plant cells does
    not permit cytokinesis by furrowing
       Begins with formation of a cell plate which
        eventually becomes new plasma membrane
        between the daughter cells




                      Mader; Biology, 9th Ed.
Cytokinesis in Plant Cells




         Mader; Biology, 9th Ed.
         Prokaryotic Cell Division

   Asexual Reproduction - offspring are
    genetically identical to the parent
       Binary fission produces two (binary) daughter
        cells that are identical to the original parent
          Prokaryotes contain a single chromosome with
          only a few proteins




                         Mader; Biology, 9th Ed.
Prokaryotic Cell Division




        Mader; Biology, 9th Ed.
                               Cancer
   Cancer – cellular growth disorder that results
    from the mutation of genes that regulate the cell
    cycle
   Neoplasm – abnormal growth of cells
       Benign – non-cancerous neoplasm
            Encapsulated
            Do not invade neighboring tissue or spread
       Malignant – cancerous neoplasm
            Not encapsulated
            Readily invade neighboring tissues
            May also detach and lodge in distant places – metastasis
            Results from mutation of genes regulating the cell cycle
   Carcinogenesis – development of cancer
                              Mader; Biology, 9th Ed.
    Characteristics of Cancer Cells

 Lack differentiation
 Abnormal nuclei

 Form tumors

 Undergo metastasis and angiogenesis




               Mader; Biology, 9th Ed.
Characteristics of Cancer Cells




           Mader; Biology, 9th Ed.
                       Cervical Cancer




http://rds.yahoo.com/S=96062883/K=cervical+cancer+cells/v=2/SID=e/l=IVR/SIG=12aklm0go/
                                    Mader; Biology, 9th Ed.
EXP=1127260755/*-http%3A//www.tcd.ie/Histopathology/research/cervical.htm
                              Colon Cancer




http://rds.yahoo.com/S=96062883/K=colon+cancer+cells/v=2/SID=e/l=IVR/SIG=12958nea8/EXP=1127261605/*http%
                                           Mader; Biology, 9th Ed.
3A//www.bioscience.org/2004/v9/af/1311/figures.htm
                   Origin of Cancer
   Mutations in DNA repair genes

   Mutations in proto-oncogenes and tumor-suppressor
    genes
       Proto-oncogenes promote the cell cycle in various ways
       Tumor suppressor genes inhibit the cell cycle in various ways
       Both normally regulated in coordination with organism’s growth
        plan
       If either mutates, may lose control and become oncogene


   Telomerase
                            Mader; Biology, 9th Ed.
                        Oncogenes Function
Oncogenes               src                   Tyrosine kinase
                        ras                   G protein
   Oncogene –          erb                   Epidermal growth factor
    gene that when
                        sis                   Platelet-derived growth
    altered or
    mutated, its                              factor
    product is          p53*                  Tumor suppressor
    responsible for     myc*                  Cell cycle
    transformation
    of healthy cells    Rb*                   Tumor suppressor
    into cancer cells   DHAP*                 Tumor suppressor
   Often involved
    in cell cycle       ProT*                 Blocks apoptosis
    control             PETCAM*               Tumor suppressor
                        bcl-2*                Blocks apoptosis
                        Mader; Biology, 9th Ed.
                                                  *Involved in control of cell cycle
        Tumor Supressor Genes

   Inhibitory to cell cycle
     Rb - retinoblastoma
     P53 – Li-Fraumini

   Mutations




                    Mader; Biology, 9th Ed.
Cell Cycle Control
                                Cyclins and
                                 Cyclin-
                                 dependent
                                 kinases (Cdks)
                                Function with
                                 tumor-
                                 suppressor
                                 genes to control
                                 cell cycle

     Mader; Biology, 9th Ed.
       Cell Cycle Regulation

 Balance between stimulatory and
  inhibitory pathways
 Stimulatory pathway results activation of
  proto-oncogene which stimulate cell cycle
 Inhibitory pathway results activation of
  tumor-suppressor genes which inhibit cell
  cycle

                Mader; Biology, 9th Ed.
Mader; Biology, 9th Ed.
                      Telomerase
   Chromosomes normally have excess DNA
    material at each end called telomeres
       These get shorter each cell division
       When they get very short the cell will no longer divide
   Telomerase is an enzyme that adds telomeres

   Mutations in telomerase gene:
       Keeps adding new telomeres
       Allow cancer cells to continually divide (become
        “immortalized”)


                         Mader; Biology, 9th Ed.
Mader; Biology, 9th Ed.

				
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