Bio Ch14 DNA/Genetics

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tjtolman
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140460
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Bio Ch14 DNA/Genetics
Updated:
2012-03-12 12:20:47
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Bio
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Ch 14
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  1. Where is genetic info:
    • 1930's Hammerling
    • Large cell green algae- Acetabucaria (1cell 5cm tall)
    • 1) Amputation: Take only foot, Take only stalk, take only cap... Only foot grew whole cell back.
    • 2) Grafing exp.-Took diff cells and combined them. Foot completly controls form of the cap.
    • -Nucleus in foot (maybe genetic info in foot)
  2. Transformation Exp.
    • Known-chromosomes in nucleus, chromosomes made of DNA and protein.
    • Is genetic info in DNA or protein?
    • Transformation exp- Griffith 1920's
    • Worked w/ mice and bacteria (streptococcus pnemonia)
    • Deadly sp into mouse=mouse died
    • Non pathogen mouse was fine
    • Killed bacteria= mouse was fine
    • Mixed killed bacteria w non deadly... mouse died
    • Transformation because somehow genetic info moved
  3. Transformation follow up-
    • 1944- Avery, Malled, Mccarty
    • Used mice/bacteria system
    • A) destroyed protein - no effect (mouse still died)
    • B) Destroyed DNA- changed result- (mouse alive)
    • -genetic info in DNA
  4. DNA vs Protein
    • Exp. w/ Bacteriophages (viruses that affect bacteria)
    • 1952- Hershey and Chase
    • (phage- DNA/RNA and protein) --- inject into bacterium
    • Attack, reproduce inside, come out
    • What is injected inside??
    • Labeled DNA/RNA (radioactive P32)
    • labeled protein (radioactive S35)
    • P32 made it in the bacterium. Therefore DNA entered bacterium (DNA contains genetic info)
  5. Structure of DNA
    • 1) 1869 Miesher disvoered as a chemical
    • 2) Levene - 1920's repeating unit "nucleotide"
    • a) N-containing base A,C,G,T
    • b) phosphate group
    • c) 5-carbon sugar (deoxyribose/robose)

    • P attaches to 5 prime carbon
    • N attaches to 1 prime carbon
  6. Connecting P-S-N


    • Levene thought all Nitrogen cont. bases were equal (WRONG)
    • Chargoff- 1940's found:
    • Amount of A = Amount of T
    • Amount of C = Amount of G
  7. x-ray cystalography
    • Rosalind Franklin (brittish, chemist)
    • 3 Demensional structure of molecule
    • DNA is Helical (helix)

    Watson and crick (used franklins info) - did not acknowledge her for findins. Franklin died in 1958 (acknoweledged by watson in 1968)
  8. James Watson and Francis Crick
    • Knew:
    • DNA is made of nucleotides
    • Molecullar is long - thin helix
    • Amount A:T 1:1
    • Amount C:G 1:1

    • Also knew had to be true:
    • DNA had to carry MUCH info
    • DNA had to translate info into proetein
    • DNA had to replicate itself
    • DNA had to be able to make mistakes (mutations)
  9. Watson Crick Double Helix Model
    • Distance of 1 twirl
    • width
    • Phosphate/sugars - outside
    • N-cont bases - face eachother (steps) on inside
    • Strands are anitparallel 5 to 3 3 to 5
  10. Base-pairing holds strands together:
    • A&T - 2 hydrogen bonds
    • G&C - 3 hydrogen bonds
    • Order of Nitrogen cont. bases vary.. (determines genes)
  11. Meselson and Stahl exp.
    • 1958- E. coli
    • N has weight of 15
    • N14 and N15 (N15 wieght of 15, extra neutron)
    • Grew e coli on food source included N15
    • Transfered e coli cells to N14 - measured weight of DNA
    • Heavy strands came apart and combined w/ N14.

  12. Replication
    • Complex/many enzymes
    • DNA polymerase III is main actor
    • Starts at replication origin
    • Nucleotides added in 5 prime to 3 prime direction
    • Enzyme proof reads itself in 3 prime to 5 prime direction

    • Starting place: RNA primer (where DNA III starts)
    • "RNA primase" makes RNA primer
  13. Enzymes for replication:
    • Helicase - unwinde helix (open up)
    • Gyrase- helps eliminate snarls (releives torque)
    • Single strand binding proteins- protecting single strand DNA

    • Primase- unwhinds double helix
    • Dna polly III - synthesizes DNA
    • DNA poly I- erase primer and fills gaps
    • DNA ligase- joins ends of DNA segments
  14. Summary of replication:
    • parent DNA needs to be unwound
    • Takes helicase enzymet to unwind
    • DNA gyrase unsarls
    • Single strand binding - protects single strands

    • Left w/ single strand that needs to be copied:
    • Leading strand 5 prime to 3 prime
    • Polymerse enzyme copies

    • Lagging strand done in chunks
    • RNA primer - starting point
    • Ligase seals
  15. DNA polymerse III
    • 1,000 nuc/sec proof reads
    • 5 prime to 3 direction
    • Proof reads in 3 prime to 5 prime direction
  16. Prokaryotes differences Eukaryotes
    • Pro:
    • Starts @ 1 replication orgin per chromosome
    • Bidirectional
    • No histones

    • Euk:
    • Man replicattion origins (faster)
    • Bidirectional
    • Histones assoc. w/ DNA (slower

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