DNA

• whats the link between the sugar phosphate backbone to its function ?

  the strong covalent bond creates a strong outside structure when the helix is formed
• whats the link between the double strands to its function?

  Complementary base pairing so replication can occur
• whats the link between weak hydrogen bonds to its function?

  easy unzipping of the two strands in a double helix for replication
• whats the link for it being a large molecule to its function?

  carries alot of information
• how does complimentary based pairing link to its function?

  allows identical copies to be made
• what are two key enzymes involved in dna repliction

  dna helicase dna polymerase
• what is the process of dna replication called

  semi - conservative
• who discovered the structure of dna

  watson and crick
• when did they discover the structure of dna

  1953
• what did watson and crick hypothesise

  dna replicated either conservatively or semi - conservatively
• 15 N is a dense isotope and 14 N is a light isotope
• summarise how mehselson and stahls experiment worked

  1. bacteria grown in medium with just 14N isotopes will have DNA which only contains that
  2. bacteria grown in medium with just 15N isotopes will have DNA which only contains that isotopes and will be heavier
  3. dna samples can be spun in a centrifuge to confirm its density
• what Is DNAs function?

  to carry genetic information
• what is it a polymer of?

  nucleotides
• describe the structure of DNA?

  a double helix made of two polynucleotide chains held together by hydrogen bonds between specific complimentary base pairs
• what do DNA nucleotides contain?

  • a phosphate group
  • a deoxyribose sugar
  • base : adenine , thymine , cytosine , guanine
• what bonds form between phosphate and deoxyribose?

  phosphodiester
• how many hydrogen bonds are there between adenine and thymine?

  two
• how many hydrogen bonds are between cytosine and guanine?

  three
• how does DNA replicate?

  semi-conservative replication
• describe semi-conservative replication

  1. DNA helicase breaks hydrogen bonds between complimentary strands
  2. DNA helix unwinds
  3. each strand acts as a template
  4. free floating nucleotides in the nucleus are attracted to their complimentary based pair on the parent strand
  5. DNA polymerase joins the adjacent nucleotides via condensation reaction forming phosphodiester bonds
• which scientists discovered how DNA replicates?

  meselson and stahl
• what is an advantage of semi-conservative replication?

  ensures genetic continuity between generations of cells