How to Extract and See DNA for Cheap

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Introduction: How to Extract and See DNA for Cheap

Scientific Method Contest

Fourth Prize in the
Scientific Method Contest

Here's a fun and easy experiment that I remember doing in biology class my softmore year and you can do it to at home 

Question: can an average person extract and physically see DNA?

Hypothesis: I think it is possible because all the items needed to do this can be accessed at home for cheap.

Test: you can extract DNA by breaking down the multiple layers that make up a cell first you break Down the cell membrane using liquid dish soap, the soap works by breaking down lipids that the cell membrane is made out of, when the membrane breaks all the organelles fall out of the cell, but the one we want is the nucleus this protects the DNA inside so to break that you use rubbing alcohol to break apart the protein based nucleus freeing the DNA. The DNA will float to the top because the mixture it is in is denser than the DNA.

Cells: the type of cells we will be using are Prezwaregalopigas cells, otherwise known as cheek cells because they have almost no organelles and are constantly coming loose.

Step 1:

Gather the following: sodium chloride, liquid soap, some glassware , bottled or distilled water, 2 cups with lids, a pen, and rubbing alcohol 

Step 2:

Place 8 grams of sodium chloride in one of the glasses and dissolve with 92 milliliters of water. 

Step 3:

In a second glass, combine 25 milliliters of liquid soap with 75 milliliters of water. 

Step 4:

Pour 10 milliliters of the water into a plastic cup and swirl the water in your mouth for 30 seconds. Then you spit it in to the Salt solution 

Step 5:

Now you combine the two mixtures in the cup with the lid. Next Add 5 milliliters of the rubbing alcohol to the test tube making sure to pour it at an angle down the side of the cup with the lid. Finally you shake it for 5 minutes

Step 6:

After shaking you let it sit for 3 more minutes. What you will see is a white substance in clumps on top of the of the mixture, this is your DNA. You can use a popsicle stick to take it out.

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13 Comments

Hmm... Do you have to call sodium chloride? You can call it table salt right?

Table salt has an anti-caking compound added, plus iodine which was added in the 1930s for health reasons in the US. So, no, you can not say table salt, sea salt and kosher generally lack the additives, does hurt to check the label on kosher. Table salt, sea salt, kosher salt all come from the sea at some point, even if found in the ground. Interesting isn't it, sea salt usually cost more at an upscale store then a processed table salt. The gullibility of the US consumer and marketing. If you tried using a neti pot with table salt that iodine is going to burn, pure sea salts works, not sure about the anti-caking up your nose :) I don't think it matters here much, but, yes there is a difference you should know about

For an experiment as simple as this, ordinary table salt works just fine. I just finished running dozens of DNA-from-spit demos at Maker Faire last weekend, and it's pretty foolproof, regardless of what salt or detergent you use.

I usually ask people to collect about 1ml of pure spit (~1/2 inch liquid in a 5ml Falcon tube). Then add one drop of dishwashing detergent. Invert to mix. Add a sprinkling of table salt. Invert to mix. Then fill the rest of the tube with rubbing alcohol to extract the DNA. Works every time. No measuring necessary, and since you start with a large amount of spit, you get tons of DNA.

The usual chemical name for NaCl is "Common Salt", but there are many compounds that are called salts. Table Salt does have additives in it, but here in the UK "Cooking Salt" is about as pure as you are likely to need, and considering the fragrances, preservatives and other additives in the "Dish Soap" (which I'm guessing that's actually DETERGENT anyway). I think a little of the "Anti Cake" additives are not likely to affect the result. Iodine might, depending on the concentrations.

um yes hello, im a common simpleton who has never seen this done and lacks the will to do the simple google search to disprove my own opinions, but im somehow an expert on this matter. that said, nay NAY! NAY I SAY. jk, great instructable. so sad that devils avocates speckle this site like a disease. keep it up. voted for scientific method contest.

just so you know

dna cant even be seen through a microscope

. November 30, 2012 this was the date the first microscope image was taken and just so you know! In large quantities any thing can be seen, if you take a grain of sand just one and place it on a table then stand 10 feet away you won't be able to see that one grain now if you had a bunch of sand you could see it from 10 feet away, if not farther. So there you go another fun fact to tell your friends.

here's my evidence, hopefully this is enough to convince you.

dna-double-helix.jpg

No offense meant, but how are you so sure that the white thing is DNA and not some fatty acid coagulation or something weird that gets precipitated?