Chapter 13 & 14 Vocabulary & Important Concepts

• Frederick Griffith


  Discovered transformation while searching for how bacteria made people sick
• Griffith's Experiment


  Experimented with harmless rough strain bacteria and pneumonia-causing S strain bacteria; dead S strain can make R strain dangerous by altering its genes (transformation)

  
• transformation


  process in which one strain of bacteria is permanently changed by genes from another strain
• Oswald Avery


  Discovered that DNA stores and transmits genetic info
• Avery's experiment


  Avery treated biological molecules (ex. nucleic acids, lipids, etc.) with enzymes to destroy them; transformation does not occur without DNA
• Alfred Hershey and Martha Chase


  further proved that DNA is the molecule of genetic material
• Hershey-Chase experiment


  An experiment involving bacteriophages, which a component of enters the bacteria to transfer its genetic material; Radioactive phosphorus-32 marked DNA and sulfur-35 marked proteins; Phosphorus-32 was found in the supernate of the bacteria - the DNA entered the bacteria to transfer its genetic material

  
• bacteriophage


  a kind of virus that infects bacteria

  
• nucleotides


  the basic building block of nucleic acids

  
• nitrogenous bases


  adenine, thymine, uracil, guanine, cytosine

  
• two types of nitrogenous bases

  purines and pyrimidines

  
• purine


  double-ring nitrogenous base; adenine and guanine

  
• pyrimidine


  single-ring nitrogenous base; thymine and cytosine

  
• Chargaff's Rule


  [A] = [T] and [C] = [G]
• Rosalind Franklin


  Used X-ray diffraction to photograph DNA; the photo allowed Watson and Crick to build a model of DNA

  
• Watson and Crick


  Used Franklin's x-ray photo and Chargraff's Rule to produce a model of DNA
• Watson and Crick's model


  double helix (as in Franklin's photo); purines hydrogen bonded to pyrimidines (explains Chargraff's rule); sugar-phosphate backbone; antiparallel
• 5' (five prime)


  End of the DNA strand where the fifth carbon is bonded to the phosphate group
• 3' (three prime)


  End of the DNA strand where there is no phosphate group
• hydrogen bonds in DNA


  hold base pairs together; weak enough to split the double helix for replication
• Number of hydrogen bonds between A and T

  two
• Number of hydrogen bonds between G and C

  three
• complementary


  bases are paired in a specific way that fits its counterpart

  ex. original has A, complementary has T
• Structure of DNA and replication


  Double helix and complementary base pairing facilitate replication
• replication


  process of copying DNA that occurs during the S (synthesis) stage of interphase; used to duplicate DNA for cell division

  
• origin of replication


  Site where the replication of a DNA molecule begins; typically in area rich with A-T pairs b/c its 2 hydrogen bonds are weaker than G-C's 3

  
• replication bubble


  Region of DNA where helicase has split the double helix

  
• helicase


  enzyme that unwinds DNA by breaking hydrogen bonds; results in replication bubble, replication forks, and ssDNA
• ssDNA


  single-stranded DNA; unwound DNA
• SSB


  single-stranded binding proteins; stabilizes ssDNA by keeping the strands apart (they were unstable b/c they want to become the double helix again)

  
• RNA primase


  Enzyme that adds RNA primers

  
• RNA primer


  short segments of RNA nucleotides (about 10) that are complementary to the DNA; needed because DNA polymerase needs a foundation to add on; initiates addition of DNA nucleotides

  
• DNA polymerase III


  Enzyme that adds nucleotides to the 3' side of the template strand (new strand is made from 5' to 3' b/c they are antiparallel); proofreads new DNA

  
• template strand


  Original strand that the new strand complements
• reason for leading and lagging strands


  Nucleotides can only be added to the 3' end of the template strand, but the strands are still antiparallel
• leading strand


  New strand where nucleotides are added continuously (toward replication fork)

  
• lagging strand


  New strand where nucleotides are added discontinuously (away from replication fork); segments of RNA primer added (RNA primase more active), then Okazaki fragments added

  
• Okazaki fragments


  Fragments of DNA (~100-200 nucleotides) added to the lagging strand

  
• semiconservative


  describes DNA replication; in each new DNA molecule, there is one original strand and one new strand

  
• DNA polymerase I


  Enzyme that replaces RNA primer with DNA in the lagging strand; exonuclease removes RNA primer