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DNA Extraction and Fingerprinting


									DNA Extraction
            Getting the DNA
• Most biotechnology (gene therapy,
  genetically modified organisms, DNA
  fingerprinting, etc.) involves the use of
  – In order to use the DNA, it must first be
    removed from the organism
  – This is known as DNA extraction
       Steps of DNA Extraction
•   DNA is contained inside all living cells
    (usually in a nucleus). To extract it,
    these steps must be followed:
    1. Isolate the cells
    2. Release the DNA from the cells
    3. Separate the DNA, proteins, and other cell
    4. Isolate the purified DNA
         1. Isolate the cells
• Some cells must be removed from the
  organism. This can be done in several
  – Cheek swab, blood sample, hair sample with
    follicle attached
  – In the DNA extraction lab we isolated the
    banana cells by blending so that the cells
    weren’t “clumped” anymore
 2. Release DNA from the cells
• DNA is well-protected within cells.
  – Most cells have a cell membrane and nuclear
  – Plant cells also have a cell wall
• A detergent is a chemical that can disrupt
  the chemical bonds that hold together the
  membranes and walls
• In our lab, detergent was in the shampoo
(DNA)              Mitochondria


  Cell Wall
  Cell Membrane
           Stop and Think?
• Which type of cell would require you to do
  more work in order to remove the DNA- a
  plant or an animal cell? Explain.
Adding shampoo to the banana mixture
  3. Separate the DNA from other
            cell “stuff”
• DNA is a nucleic acid. To isolate it, it must
  be separated from the other
  macromolecules in a cell (carbohydrates,
  lipids, and proteins)
  – Salt and detergent (shampoo) in the lab
    caused the other macromolecules to solidify
    so that they could be filtered out by the coffee
                     = solidified
                     carbs, lipids,
          +          and proteins

Shampoo       Salt

                     Only DNA is
                     small enough to
                     fit through holes
                     in coffee filter
    4. Isolate the purified DNA
• After removing carbs, lipids, and proteins,
  only the nucleic acid (DNA) was left in the
• Adding the filtrate to cold isopropyl alcohol
  caused the DNA to precipitate (solidify) so
  that it was visible
Filtrate (water + DNA)

                            DNA moves out of water into
                            alcohol layer and solidifies
               Add to cold alcohol
   Laboratory DNA Extraction
• Now, let’s see what DNA extraction looks
  like in a real laboratory
   What can you do with isolated
• Combine it with normal DNA to “fix” a
  genetic mutation (gene therapy)
• Combine it with DNA containing a
  desirable trait from another organism to
  create a new combination (genetic
• Look for patterns in the DNA (DNA

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