Core: DNA

  • Created by: jross10
  • Created on: 30-03-15 12:46
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  • DNA
    • A double helix of paired bases
      • DNA molecule has two strands coiled together in shape of double helix (two spirals)
      • Two strands held together by chemicals called bases
        • Four different bases: Adenine (A); Cytosine (C); Guanine (G); Thymine (T)
      • Bases are paired (always in the same way): A-T; C-G; called base-pairing
      • Base pairs joined together by weak hydrogen bonds
      • Gene is a section of DNA and the sequence of bases in a gene code for a specific protein
    • Watson, Crick, Franklin and Wilkins discovered DNA Structure
      • Rosalind Franklin and Maurice Wilkins
        • Discovered helical structure by directing beams of x-rays onto crystallised DNA and looking at patterns formed
      • James Watson and Francis Crick
        • Used structure along with knowledge  that  Adenine and Guanine matched amount of Thymine and Cytosine to make model of DNA molecule
    • Practical to extract DNA
      • 1 - chop some onion and place in a solution of detergent and salt
        • detergent breaks down cell membranes and salt makes DNA stick togetehr
      • 2 - put beaker into water bath of 60 for 15minutes
        • denatures enzymes that could digest DNA and softens onion cells
      • 3 - put beaker in ice to cool
        • stops DNA from breaking down
      • 4 - once mixture is ice cold put into a blender for a few seconds
        • breaks down cell walls and releases DNA
      • 5 - cool mixture again then filter to get froth and big bits of cells out
      • gently add ice cold alcohol to mixture
        • DNA starts coming out; appears as stringy white substance


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