Extracting DNA with Uncle Cecil

Extracting DNA with Uncle Cecil at the Sassafras Science blogHowdy folks – Cecil Sassafras here again!

Blaine and Tracey asked me to come by today and share with you all “something fun.” Well we all know where that can lead.

This time we will not be learning about rockets. We will be learning about something much smaller – DNA.

Blaine’s and Tracey’s journey through DNA is recorded in volume 2. But if you haven’t gotten there yet, I highly recommend this post all about DNA.

In short, DNA is the stuff that tells our cells what to do and how to look. It resides in the nucleus of a cell, so as you can imagine it is quite tiny.

In fact, you normally need a very powerful microscope to see DNA for yourself. That is, unless you extract it and force it to join up together into one giant mass of DNA!!

Today, I’m going to share with you a trick that I learned in college to make DNA visible to the naked eye. It always makes me feel like a bit like a mad scientist, so I’m sure you guys will have a blast with it.

Extracting DNA Materials

Before you begin, you need to gather up the following:

  • Sliced fruit (a banana, strawberry, kiwi, or tomato will all work)
  • Dish soap
  • Salt
  • Ice-cold Isopropyl alcohol (70% or higher)
  • Zipper-style plastic bag
  • Coffee filter
  • Funnel
  • Wooden coffee stirrer
  • Test tube (or clear glass) for the extraction process

Extracting DNA Procedure

Now we get to the real fun!!

We are going to breakdown some cell walls and cause the DNA to head out into the solution. Then we will use some alcohol to force the DNA to join up into large chains that we can actually see.

Let’s begin!

Step 1 – Make the extraction solution.

  1. Measure out 240 mL of water (about ½ cup).
  2. Add 35 mL of liquid dish soap (about 2 TBSP) and 5 grams of salt (about 1 tsp).
  3. Mix well and you have your extraction solution.

Step 2 – Breakdown the cell walls so that the DNA can be released.

  1. Add about a several slices of fruit to the baggie – about a third of a banana or one full strawberry will do.
  2. Use your hands mash it up. You are mechanically breaking down the fruit.
  3. Then, add 15 to 30 mL of extraction solution (about 1 to 2 TBSP). Now, you are chemically breaking down the cell walls in the fruit.
  4. Keep squishing for about a minute or so to make sure that some of the DNA is released into the solution. If you have time, you can let the mixture sit for ten to fifteen minutes so that even more DNA is released.

Step 3 – Remove the solids.

  1. Line the funnel with the coffee filter and place the funnel in the test tube.
  2. Then, pour the contents of the baggie into the lined-funnel and gently squeeze the liquid into the test tube. You want the tube to be about a quarter- to a third-of-the-way full.

Step 4 – Extract the DNA!

  1. Slowly pour 30 to 45 mL of the ice-cold alcohol (about 2 to 3 TBSP) into the test tube, so that you create a layer of alcohol resting on your fruit layer.
  2. Watch what happens. You will see something that look cotton fluff start to appear, this is DNA!
  3. You can use the wooden coffee stirrer to gently stir the solution and collect some of the DNA material so you can view it up close like below.

extracting DNA pic

Even More Fun with DNA

The twins are always asking for more, so here are two ideas you can use to take extracting DNA to the max:

  • Try different kinds of fruit (like grapes) or veggies (like an onion) to see if the DNA yield is more or less.
  • You can also try extracting some of your own DNA by swishing a little water around in your mouth. Then, spit the liquid out into a bag. Add the extraction solution and follow the procedure as before.

Well I hope you will enjoy extracting your own DNA! See ya next time . . .

by Cecil Sassafras

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