CH 10: How Cells Divide

CH 10: How Cells Divide

1. BACTERIAL CELL DIVISION

   • bacteria divide by BINARY FISSION
     • reproduction is clonal

2. EUKARYOTIC CHROMOSOMES

3. CHROMOSOMES

   • made of chromatin
     • complex of DNA and protein
   • NON-DIVIDING NUCLEUS
     • HETEROCHROMATIN not expressed
     • EUCHROMATIN expressed
   • CHROMOSOME STRUCTURE
     • NUCLEOSOME
       • complex of DNA and histone proteins
         • HISTONES
           • positively charged, strongly attracted to negatively charged phosphate groups of DNA
       • promote and guide coiling DNA

4. Eukaryotic Cell Cycle

   • INTERPHASE
     • G1 (gap phase 1)
       • primary growth phase, longest phase
     • S (synthesis)
       • replication of DNA
     • G2 (gap phase 2)
       • organelles replicate, microtubules organize
   • DURATION
     • typical mammal cell around 24 hours
   • M PHASE
     • M (mitosis)
       • subdivided into four phases
         • PROPHASE
           • chromosomes condense, centrioles migrate to opposite ends, nuclear envelope breaks down
         • PROMETAPHASE
           • spindles attach to kinetochore of sister chromatids
         • METAPHASE
           • chromosomes align at metaphase plate
         • ANAPHASE
           • cohesion proteins removed, spindle fibers are shorter, chromosomes pulled to opposite poles
         • TELOPHASE
           • nuclear envelop reforms around each set of chromosomes, chromosomes uncoil, spindle apparatus diassembles
       • division of nucleus
     • C (cytokinesis)
       • separation of new cells

5. CANCER

   • uncontrolled cell division
   • WHY?
     • FAILURE IN CELL CYCLE CONTROL
       • TUMOR-SUPPRESSOR GENES
         • make proteins to stop cell cycle
         • "BREAK PEDAL"
         • P53
           • P53 protein monitors integrity of DNA: if it is damaged or not, if it can be repaired
           • if it can't be repaired
             • APOPTOSIS
               • cell is programmed to kill itself
           • LOSS OF FUNCTION
             • cells will divide without repair
               • then there is build up of multiple mutations
                 • CANCER
             • two tumor-suppressor genes need to lose function
       • PROTO-ONCOGENES
         • tells cell cycle to go
         • "GAS PEDAL"
         • GAIN OF FUNCTION
           • ONCO: rapid cell divison / cancer
           • only one oncogene needs to have uncontrolled division
       • MUTATIONS CAUSE THESE GENES NOT TO WORK

6. CELLS PRODUCE MORE CELLS FOR GROWTH AND REPAIR

Images and files in the map