- [Instructor] Precipitate
the DNA from solution by adding an equal volume of
100% ethanol to each sample. And mix by inversion 10 times. The solution may become cloudy. This is normal. After incubating at room
temperature for five minutes, place the samples in the microcentrifuge with the hinges facing outward. Remember to balance your tubes. Spin the samples for two minutes. Remove the tubes from
the centrifuge gently, being mindful not to disturb the pellet, which now contains your DNA. Visually inspect for a pellet
at the bottom of the tube on the side of the hinge. A pellet is not always visible, so you can choose to centrifuge
again or proceed as normal. In this example, a pellet is
only seen in samples C and D, but all samples are carried
through the process. Using a P1000, slowly remove
and discard approximately 800 microliters of supernatant. Place the tip at the bottom of the tube on the opposite side of the
pellet to avoid disturbing it. It is not important at this point that all solution is removed. Just get as much as possible. Expel the tip with the solution inside into the discard bucket. Repeat this process for
all remaining samples. Visually inspect the tube to see if this pellet is still present. If it has gone missing,
make a note of that. Clean the DNA pellet by
adding 250 microliters of 70% ethanol to each sample. Do not mix the solution,
as it is imperative that the pallet is not disturbed. Repeat this process for
all remaining samples. Place the samples in the centrifuge, being mindful of balance,
and spin for two minutes. Remove the tubes from
the centrifuge carefully. In this step, the pellet
still contains the DNA and it is important to
remove as much supernatant as possible without disturbing the pellet. So remove and discard the supernatant using the P200 for precision. This will take two or more draws. On the first draw, you
can expel the solution into the discard bucket and use the same tip to draw up again as long as the tip has not
touched other surfaces. Repeat this process for
the remaining samples. Lay out a few layers of Kimwipes. Open the tube and knock
it onto the Kimwipe to remove any large volumes
of solution still remaining. Leave the tube open and lay
it on its side to evaporate any of the remaining
solution from the pellet. Repeat this process for
all remaining samples and allow them to air
dry for 20 to 30 minutes. If the tube still has spots of solution or if the pellet does not look dry, allow for evaporation to continue. If the pellet looks dry, then re-suspend the DNA using water. Add 100 microliters of
molecular biology grade water directly onto the pellet's side. Cap the tube and mix by
vortexing for a few minutes. Visually inspect the tube to ensure that the pellet has disappeared or
has gone back into solution. If it has not, then continue to vortex or allow the tube to
sit at room temperature before proceeding to subsequent steps. Repeat this for all remaining samples.
