Bio CH 16

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Anonymous
ID:
84019
Filename:
Bio CH 16
Updated:
2011-05-05 16:56:42
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FML
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Final
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  1. Experimental support for DNA as genetic material
    • Watson/Crick first to discover double-helix DNA
    • -Based on Rosalind Franklin's X-Ray images
  2. Complementarity DNA structure
    • A:T
    • G:C
    • Why? can only form H bonds with specific parter
    • also, Purine: purine would be too wide (ex A:G)
    • Pyrimidine: pyrimidine too narrow (ex: C:T)
  3. Antiparallel strands DNA structure
    • Strands of DNA are antiparallel
    • One strand is upside down to the other
    • Sugar-phosphate backbones run opposite
    • 5'->3' direction opposite for each strand (upside down)
    • 5' or 3' named for carbon number of sugar
    • -Deoxyribose is a 5C sugar
    • -Terminal 5' attatched to phosphate group
    • -Terminal 3' attatched to hydroxyl group
  4. DNA replication
    • Base pairing enables DNA replication
    • -Existing strand serves as template for copy
    • -Strands are complementary
    • Semiconservative
    • 2 strands found in parent molecule
    • 1 parent strand into each daughter molecule
    • 1 new strand build in each daughter molecule
    • Enzymes and proteins carry out replication
    • Replication begins at specific sites (called origins of replication)
    • Strands Separate->Replication Bubble(s)
    • Bubbles expand and fuse in both directions
    • Replication fork at each end of bubble
  5. strand elongation in DNA replication
    • DNA polymerases
    • -Enzymes that catalyze DNA elongation
    • -Nucleotides added according to template
    • DNA polymerase can only add to 3' end
    • -DNA elongates in a 5'-->3' direction
    • -50 Bases/second in human cells
    • Strand built with nucleoside triphosphates
    • -Nucleotide with three phosphates
  6. Leading and lagging strands in DNA elongation
  7. Proofreading and repair
    • Mismatch repair in replication
    • -1/10000 nucleotides wrong initially
    • -1/1,000,000,000 after proofreading
    • --------DNA polymerase proofreads itself
    • Repair damage in existing DNA
    • -Chemical (metabolic byproducts, environment), UV light, radioactivity etc.
    • -Nuclease cuts out damaged DNA
    • DNA polymerase fills gap
    • DNA ligase reconnects strand
  8. Telomeric DNA
    • Protects from gene erosion
    • Telomers may affect organismal life span
    • --Limits number of cell divisions (somatic cells)
    • --Could protect against cancer cell division
    • ----Although some cancers can stabilize telomeres
    • Telomerase: restores shortened telomeres
    • ----Only present in germ cells-->gametes
  9. Hierarchy of DNA organization
    • 1. DNA double Helix
    • 2. DNA + histones
    • ---proteins for organizing DNA
    • 3. Nucleosomes
    • ---"Beads on a string", histones wrap DNA
    • 4. Chromatin fibers- linked nucleosomes
    • 5. Looped domains of chromatin
    • 6. Condensed chromosomes (dividing cells)

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