DNA Isolation from Onion!
Today, the students are going to isolate DNA from onions. You will need a blender or a food processor for this experiment. If you do not have one, check to see if your teacher does. If neither of you have one, then let me know ahead of time, and I can provide one from my home. You will also need to bring a knife and cutting board to cut the onions as well as a measuring cup. All other materials will be provided.
The first part of the DNA experiment is to grind up the onion, which is followed by a short incubation and a slow filtering step. The best strategy is to blend first, and then lecture while incubating and filtering. After the lecture, you can then finish the DNA preparation.
1 knife sharp enough to cut an onion and cutting board*
½ cup water (may need a bit more)
¼ cup liquid soap
isopropyl alcohol (99%, aka rubbing alcohol)
DNA structure overhead (see last page to get an idea of how this will look.)
*You must provide these items.
Experimental Details, First Part
Peel and cut up two onions, and place onions in blender. The onions do not need to be in tiny pieces, cutting into eighths should be fine. Let students help put onions into blender, they can break up layers a bit, and then ask them to rinse their hands. Now, add water. ½ cup should be enough, but if you are having trouble blending, add a little more. Turn on blender, and finely chop up the onion. This will not take too long; if you puree the onion too finely, then the filtering step will be slow. I just get all chunks blending, and then blend for about 5 more seconds. Let students see this yummy onion smoothee!!! It’s a bit smelly so they may not want to be too close for too long. After all is blended, pour into yogurt container, add ¼ cup liquid soap, and let some students stir gently. This can become a foamy mess if stirred...
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