Polynucleotides + DNA

Subdecks (1)

Cards (21)

  • Describe and explain the steps in extracting DNA
    • Blend (homogenise) sample with salt + distilled water to break cells apart from each other.
    • Sit in detergent for 5-10 minutes - Disrupt cell membrane
    • Add protease (+RNAse) to break down histones and separated DNA from proteins.
    • Filter and add ice cold ethanol at 45 degrees to form a layer.
    • Extract Dna (white precipitate) using a stick inbetween the solution and ethanol.
  • Nucleotides join together to form polynucleotides.
  • The nucleotides join up between the phosphate group of one nucleotide and the sugar of another via a condensation reaction. This forms a phosphodiester bond.
  • A phosphodiester bond consists of a phosphate group and 2 ester bonds.
  • The chain of sugars and phosphate is known as the sugar-phosphate backbone.
  • Polynucleotides can be broken down into nucleotides again by breaking the phosphodiester bonds (using hydrolysis reactions).
  • Two polynucleotide strands join together to form a double-helix.
  • Two DNA polynucleotide strands join together by hydrogen bonding between the bases. Each base can only join will one particular partner - this is called complementart base pairing.
  • Adenine always pairs with thymine (A - T) and cytosine always pairs with guanine (C - G)
  • Adenine and Guanine are both purines which always pair with pyrimidines
  • Cytosine and thymine are both pyrimidines which always pair with purines.
  • Two hydrogen bonds form between A and T, and three hydrogen bonds form between C and G.
  • Two antiparallel polynucleotide strands twist to form the DNA double-helix.
  • DNA copies itself before cell division so that each new cell has the full amount of DNA.