DNA Fingerprinting/profiling

A quick mindmap to show DNA profiling/fingerprinting via PCR and gel electrophoresis

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  • DNA Fingerprinting
    • PCR
      • Reactants: DNA samples, DNA polymerase,the four nucleotide bases and primers
      • The reactants are placed in a vial
      • The mixture is heated to 90-95'C
        • This is done to separate the two DNA strands as the hydrogen bonds break down
      • The mixture is cooled to 50-60'C
        • This causes the primers to bind (anneal) to the single DNA strands
      • The mixture is reheated to 75'C - the optimum temperature for the enzyme to build the complimentary strands of DNA
    • Gel Electrophesis
      • The DNA fragments are each put in their own well of the agarose gel
      • The agarose gel is completely covered with a buffer
      • an electrical current is passed through the apparatus and the DNA fragments move towards the negative anode
      • One the process is complete the gel is left in a dye and the dye is the rinsed off
        • This process dyes the DNA fragments, it become even clearer if the gel block is placed on a light box
    • Prep
      • DNA extracted from sample
      • The DNA is split into fragments using restriction enzymes
      • differenty restriction enzymes cut at different recognition points
    • Southern blotting
      • An alkaline buffer solution is added to the gel after electrophoresis
        • A nylon filter is placed over it
          • Dry, absorbent paper is used to draw the solution containing the fragments from the gel to the filter leaving 'blots'
            • The alkaline solution also denatures the fragments so the strands separate and the base sequences are exposed
    • DNA
      • Introns are sections of non-coding DNA that are unique to each person, therefore can be used in DNA profiling
      • Mini-satellites
        • 20-50 long base sequence repeated from 50 to several hundred times
      • Micro-satellites
        • 2-4 bases long sequence that is repeated between 5 and 15 times
      • The more closely related two individuals are, the more similar the DNA patterns are


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