DNA Extraction: What happens to the stuff we scrape off your cheek?
Posted 3/22/2011 12:03 AM by Nicole Garneau | Comments
It's been really busy in Lab Central! Staff and volunteers have
been enrolling curious and science-hungry visitors in Genetics of
Taste: A Flavor For Health like crazy! As of today, we've enrolled
931of participants in our research study and counting! That means
we have 931of samples that need DNA extraction!
In this photo you'll see tubes of DNA collected so far:
Take a look at the cell above. The nucleus is the cell's command
center; shown here as the large center circle. Inside that nucleus
is DNA, and it's telling your body how to make you! In an earlier
blog post, Nicole explained that in the research study we swab the
inside of a participant's cheek in order to get cells which contain
We want to visualize a specific section of the DNA that contains
the gene TAS2R38. This gene helps determine whether or not you have
the genetic ability to taste the bitterness in vegetables like
broccoli and spinach. But how do museum scientists actually get the
DNA from inside the cells?
STEP 1: Rupture the Cell
The cheek cell sample on the swab is placed in a tube filled
with lysis buffer. "Lysis" is an old Greek word that means "to
separate." Lysis buffer is like soap, and it ruptures the cell by
disrupting the cell membrane. This step lets all the
components inside the cell (like fats, proteins and DNA) float into
STEP 2: Purify the DNA
We want to make sure our DNA samples are really clean, meaning
that there's no cellular "junk" floating around in the tube. So to
do this, we add a solution that has a lot of salt in it. The salt
helps precipitate fats, proteins, and other cell debris out.
STEP 3: Isolate
So the last thing we do to get a nice little pellet of DNA is
add to alcohol. Why alcohol? DNA is insoluble (meaning that it's
incapable of being dissolved) in alcohol. So when we add alcohol to
our DNA sample and then centrifuge it (spin it super fast), all the
DNA is forced to the bottom. We can then siphon off the alcohol,
dry the DNA pellet, and then re-dissolve it in water.
So take a look at that. It's kind of hard to see, but that
little smudge on the bottom of that tube is DNA! This DNA sample is
then the basis for further genetic analysis.
Don't touch that dial folks; later I want to tell you what we do
with visitor DNA after extraction!
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