Question: When you “extracted” DNA, y......... Edit
Dead cells are continually being sloughed off on both the inside and outside of the body. Recently
sloughed cells still contain their nucleus and their DNA genetic material. This DNA can be collected and
traced to a specific individual. Detergents dissolve and break down the lipids (fats) and proteins that form
the primary cell membrane and disrupt the bonds that hold the membrane together. The cell contents,
including the nucleus, are thus released and become available for further treatment or isolation. Sodium
lauryl sulfate is an active ingredient in detergents. The final step of this experiment requires alcohol. The
dissolved DNA will precipitate when it comes in contact with the alcohol because it is not very soluble in
alcohol. If the procedure is done properly, fine, long strands of DNA will form at the interface where the
dissolved DNA and alcohol comes in contact. It can then be easily spooled onto a glass stir rod.
A. Obtaining the cheek cells 1. Take a small drink of water from a nearby drinking fountain and swirl it
around in your mouth several times (without swallowing) and then spit the water into the cup. 2. Bring
the cup containing the water and your cheek cells into the lab and pour a few mL into the larger test tube.
3. Add 20 drops (1mL) of the 8% NaCl (aq) to the larger test tube.
B. Releasing the DNA from inside the cheek cells In this step, the cell membranes will be removed
from the cheek cells using dish detergent. The dish detergent breaks down the cell and nuclear
membranes and releases the DNA into the salt solution. 1. Add 20 drops (1mL) of the 25% liquid
dishwashing detergent solution to the “cheek” mixture in the large test tube. 2. Stopper the test tube and
mix the contents of the tube by gently inverting the test tube several times. Do not shake the test tube.
C. Precipitate the DNA 1. Holding the test tube at a slight angle, carefully add 5mL of 95% ethanol
down the side of the test tube so it forms a layer over the cheek mixture in the test tube. 2. Hold the test
tube in an upright position for one minute and observe what happens at the interface between the ethanol
and the cheek solution.
D. Collect the DNA 1. Add 20 drops (1mL) of 95% ethanol to the smaller test tube. 2. Place a clean glass
stirring rod in the test tube containing the DNA. Collect the DNA by winding it on the rod by turning the
rod in one direction. 3. Carefully remove the rod and DNA from the solution and transfer it to a small vial
containing approximately 1mL of 95% ethanol. Observe the DNA strands floating in the alcohol. 4. Label
your DNA and keep it! Edit
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