(Optional): Isolate DNA using Household Materials
If you are feeling EXTRA, this activity guides you on how to isolate DNA from either cheek cells or banana.
This activity utilizes commercially available products. Please perform the activity in a location with very little human traffic and/or away from little humans.
Materials Needed
- 1 clear cup
- isopropyl/ ethyl alcohol at least 70% (place in freezer overnight)
- half a banana (alternatively, 3 grapes or 2 strawberries or 1 kiwi)
- table salt (iodized or uniodized)
- coffee stirrer/popsicle stick/ any thin material for stirring
- drinking water
- dishwashing liquid
- food coloring (optional)
- toothpick
- 1 coffee filter
Procedure (Just choose 1)
A. DNA Isolation from Cheek Cells
1. Fill half a 12-oz cup (~50 ml) with drinking water.
2. Dissolve 2 tbsp of salt in the water.
3. Gargle the saline solution for at least 30s (the longer you gargle, the better). Do not do this immediately after brushing although a clean mouth (i.e. not after eating) is good for this activity. Spit out the gargled solution in 1 clear cup.
4. Gargle another batch of saline solution and spit it out in the same clear cup.
5. Add 2-3 drops of dishwashing liquid. Gently stir the dishwashing liquid in the solution. Do not vigorously stir the solution to avoid creating too much foam.
***Optional: You can add 1 small drop of food coloring to the solution at this point.
6. Slowly add an equal amount of ice-cold alcohol through the walls of the cup, you should be creating an interface. DO NOT MIX the solutions together!
7. Let the solution stand for at least 1 min. You should observe white filamentous materials or mucus-like fibers at the interface. This is your DNA!
📷 Take a photo of your result.
8. If you want to save your DNA material, you can spool the fiber with a toothpick and place it in a vial filled with alcohol.
B. DNA Isolation from Banana
1. Take half a banana and place this in a ziplock bag. Mash the banana until it looks homogenous (like baby food).
2. Dissolve 2 tbsp of salt in half a 12-oz cup (~50 ml) of drinking water.
3. Add 2-3 drops of dishwashing liquid in the saline solution.
4. Add the saline solution with dishwashing liquid to the banana mash.
5. Further mash the banana with the saline solution until the contents look homogenous (sloppy baby food at this point).
6. Using a coffee filter, filter this mixture and collect the filtrate in a clear cup. Try to extract as much of the liquid as possible. Your filtrate should look like a clear, yellowish/brownish solution.
*** Optional: You can add a drop of food coloring to the filtrate at this point.
7. Carefully add an equal amount of ice-cold alcohol along the walls of the cup. DO NOT MIX! You should be creating an interface.
8. Observe the formation of white or mucus-like filaments in the interface. This is the plant DNA!
📷 Take a photo of your result.
9. You can choose to keep your DNA sample by spooling the filaments with a toothpick and keeping it in a vial containing alcohol.
📷 Take a selfie of yourself with the set-up. Share your findings and experience to the rest of the class here :)
***
🤔 Thought Questions
- How does the DNA look like?
- How do you think the reagents used were able to facilitate DNA precipitation?
- What does the procedure used for isolation and the resulting DNA say about the DNA structure?