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January 25, 2010

Extracting DNA from our cheeks

We learned how to extracted DNA from our cheeks while at the Museum of Science and Industry last week. This was fun to watch so we've decided to try this at home.

You'll need:
  1. Dawn Dish Soap (I'm sure that any dish soap will work, but Dawn [original] was highly recommend.)
  2. Salt
  3. Rubbing Alcohol (70%)
  4. cups (one for each child)
  5. water
  6. test tubes (one for each child)

Prep Work:
REFRIGERATE the (Dawn) Dish Soup and FREEZE the Rubbing Alcohol. The rubbing alcohol doesn't actually freeze, it will still be a liquid after being in the freezer. The dish soap will also be still be pour able after being in the refrigerator. We were told that we would receive better results when the dish soup as been REFRIGERATED and the Rubbing Alcohol as been "FROZEN".

The other thing that is important to know in prepping for this experiment is that you can NOT eat or drink for 2 hours prior to extracting the DNA. Not eating or drinking for at least 2 hours also helps produce better results.

FYI: The test tubes we are using came out of our microscope kit. When we were done we did look at the DNA under the microscope. It did give us a close up view of DNA, but did NOT allow us to actually see the DNA helix. The DNA helix can only be observed by a photograph taken through x-ray crystallography. That is beyond what our little home Kitchen-Science Lab can do!

Doing the Experiment:
  • pour about 4 heaping spoon full of salt with about 1 cup of water and mix.

  • pour small amount of this salt water solution into a cup (about 1-2 ml)

  • Now swish this salt solution in your mouth for about 1 minute. When you are done spit it back into the cup.

  • Transfer some of the spit from the cup into the test tube. (We are using 10 ml test tubes so we put about 2-3 ml of spit into the test tube. So in other words about 1/4-1/2 full of spit)
  • Add about 4-5 drops of dawn dish soap into the test tube with the spit.

  • Now for about 2 minutes mix the dish soap and spit in a back and forth motion.

  • Now fill the rest of the test tube with the rubbing Alcohol

  • Now for about 2 minutes do the same back and forth motion as you did earlier.

  • You should then start to see what looks like little strings of pasta in the test tube. This is your DNA.

It should clump together, but it also might be individual strains floating about. You may have to hold them near a light to see the stains, especially if they do not clump together. The pictures of the DNA in the tubes did not turn out the best.

Web-princess' DNA clumped together nicely, where Superstar's did not. DH observed that Web-princess test tube was a little bit more blue in color then Superstars so we think it's possible that Web-princess' had a bit more dish soap then Superstars.

Seeing it was hard to capture the DNA in stills I made a video. I hope you can see Web-princess' DNA floating around in the test tube in the video above. I tried to do a video of Superstar's DNA but because it did not clump together like Web-princess I couldn't get it in the video. When I move the test tube back and forth you can hopefully see this small whitish thing floating about. That is Web-princess' DNA.

Web-princess and Superstar had a blast doing this and now we hope that you will too! If you decided to do this experiment at home please share your results with us! We would like to see what you get!


  1. What a cool thing to see! We are going to try this.

  2. This is fantastic! I'm putting it on the to-do list!

  3. This looks like a fun experiment. I am visiting from THL and the Blogging Basics group.



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