Polynucleotides and DNA

• How nucleotides joined together?

  via condensation reaction, used to form a phosphodiester bond between the phosphate group and 2 ester bonds
• How are Polynucleotides broken down?


  via hydrolysis reaction
• What are the Chains of sugars and phosphates known as?

  sugar phosphate backbone
• Describe the structure of DNA?

  two polynucleotide strands = double helix

  joined by hydrogen bonds between the bases

  complementary base pairing (A+T/G+C)

  the 2 Polynucleotide strands are anti parallel
• how many hydrogen bonds form between A+T?


  2
• How many hydrogen bonds form between G+C?


  3
• How is DNA purified?

  break up the cells - blender

  solution of detergent+salt+distilled water

  incubate in water bath 60 degrees for 15 min

  ice bath to cool, then filter

  add protease enzymes

  add RNase enzymes

  dribble cold ethanol down side of tube

  wait

  white precipitate forms
• role of detergent?


  breaks cell membrane
• Role of the salt?

  binds to DNA and causes it too clump together
• why 60 degrees water bath?


  temperature should stop the enzymes from working and breaking down the DNA
• role of protease enzymes and RNase enzyme?


  Protease: Breaks down proteins. RNase: breaks down RNA
• what are the stages of synthesis of DNA by semi conservative replication?


  DNA helicase breaks hydrogen bonds between DNA strands, Helix unzips forming 2 single strands.

  The original strands act as a template.

  Free floating DNA nucleotides join to exposed bases by complementary base pairing.

  DNA polymerase joins the nucleotides on new strands together forming sugar phosphate backbone.

  Hydrogen bonds form between bases on the original and new strand.

  Double helix reforms.

  Each DNA contains one new strand and one original one.