If we could zoom in on a single, tiny cell, we could see an even teenier “container” inside called a nucleus. It holds a stringy substance: the DNA. DNA contains a code for how to build a life-form and put together the features that make that organism unique. If we remove DNA from millions of cells, however, we will be able to view it without a microscope. That is what we will do today!
• One ripe banana
• Half cup of water
• Teaspoon of salt
• Resealable zip-top bag
• Dishwashing soap or detergent
• Rubbing alcohol
• Coffee filter
• Narrow glass
• Narrow wooden stirrer
• Place your bottle of rubbing alcohol into the refrigerator or freezer and let it chill for the duration of this experiment.
• Peel a banana.
• Put the peeled banana in a resealable zip-top bag and close the bag.
• On a hard surface like a tabletop or kitchen counter, mush the banana in the bag for about a minute until it has a fine, puddinglike consistency and until all lumps are gone.
• Fill a measuring cup with a half cup of hot water and a teaspoon of salt.
• Pour this saltwater into the bag, and close the bag. Gently mix and slosh the saltwater and mashed banana together for 30 to 45 seconds.
• Add a half of a teaspoon of dishwashing detergent or dish soap into the bag. Again, mix around the contents gently. You do not want the mixture to become too foamy.
• Place the bottom half of a coffee filter in a clear glass cup. The top part of the filter should be folded over the rim of the glass to keep it in place.
• Carefully pour the contents of the bag into the filter and let it sit for several minutes until all of the liquid has dripped down into the cup. (You can now throw out the coffee filter and its contents.)
• Take the rubbing alcohol from the refrigerator. Tilt the glass and slowly pour the alcohol down the side of the cup until there is a layer that is 2.5-5 cm thick. You want to keep the alcohol and the liquefied banana as separate as possible, so complete this step slowly.
• Let this two-layered mixture sit for eight minutes. During this time, what do you see happening between the alcohol and the banana liquid layer? It looks cloudy and may have some tiny bubbles in it. The longer you wait, the more defined this layer becomes. This is the DNA pieces clumping together.
• Stick the wooden stirrer into the cup. Spin it in place so that cloudy layer spools around it. Remove the stirrer. Can you capture some of the stringy middle layer on your stirrer and remove it from the cup? The substance that you see on the stirrer is DNA!