DNA Extraction: What happens to the stuff we scrape off your cheek?

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By Devin Walecka

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 DNA.

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 the buffer.

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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