Fruit DNA Extraction

Ramisa Maliha




All living things have a set of instructions inside their cells that control the growth, repair, and multiplication of the cell called DNA. DNA stands for deoxyribose nucleic acid. The information in DNA is what defines what we are a fruit or a human!


DNA can help solve crimes! Detectives can match DNA from the crime scene to the suspects. DNA tests can also be used to determine relatives and ancestry. Modifying DNA can also help produce crops with special qualities like bigger fruits, sweeter fruits, or more resilient to bad weather.


DNA is usually wrapped up in a cell that is too small to see with the naked eye. this experiment allows the DNA to clump together so we can see!



Materials

  • 1/2 peeled ripe banana (you can also use strawberries or other fruit)

  • 1/2 cup hot water

  • 1 tsp salt

  • 1/2 tsp liquid dishwashing soap

  • resealable zip-top bag (quart size)

  • very cold rubbing alcohol (isopropyl alcohol) placed in the freezer ahead of time

  • coffee filter

  • narrow glass

  • wooden stirrer


Extracting DNA in 10 Easy Steps

  • Mash the banana in the resealable bag for about a minute until all the lumps are gone and it almost looks like pudding.

  • Pour the saltwater mix into the bag. Close the bag and very gently squeeze and move the saltwater and banana mush together. Do this for 30 to 45 seconds.

  • Add the dishwashing soap into the bag and gently mix the contents. Try to avoid making too much foam.



  • Place the coffee filter in a clear glass cup, securing the top of the filter around the lip of the cup.

  • Pour the mix into the filter and let it sit until all of the liquid drips down into the cup.

  • Remove and discard the used coffee filter.

  • Tilt the glass and slowly add cold alcohol down the side of the cup. You want the alcohol to form a layer on top of the banana mix, staying separated, so be careful not to pour it too fast. Make a layer of alcohol that is 2.5-5cm (1-2in) thick.

  • After the alcohol layer is set up, wait for eight minutes. You may see some bubbles and cloudy material moving around in the alcohol. This is the DNA pieces clumping together.



  • Use the wooden stirrer to start poking the cloudy stuff in the alcohol layer. Spin the stirrer in place to start gathering the cloudy stuff. When you are done, take a closer look at the stuff on the stirrer. You are looking at DNA!


What Happened?

You may understand that mashing a banana can break cells apart and help break apart cell walls, but why was all that other stuff added? And how did we get inside the cells and get the DNA to stick together? Let's think of three of the main items we added to the bananas.

  1. Saltwater - The salt will help the DNA strands to stick to each other in clumps large enough for you to see.

  2. Dish soap - Dish soap can help split apart the membranes (the outer "skin") that hold cells together. So when dish soap is added, the cell membrane and the nuclei are broken apart, releasing the DNA.

  3. Alcohol - The DNA clumps are soluble (can be dissolved) in some liquids, but not in alcohol. So adding alcohol helps the clumps of DNA to form.


VIDEO REFERENCE: https://www.youtube.com/watch?v=pdDP9OcqcbA

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