Seeking Sweet Polymers
Question: Will a fat red strawberry have long red DNA?
Hypothesis: We predict the DNA (polymers) of the strawberry will be similiar to the size and color of the strawberry.
Materials:
1 strawberry
1 quart size ziploc freezer bag 10 ml DNA extraction buffer test tube or small jar funnel cheese cloth or coffee filter glass rod or plastic loop made from a tie wrap 5 ml ice cold 95% isopropyl alcohol ( rubbing alcohol) Recipe for DNA extraction buffer 1 tablespoon of shampoo (without conditioner) or dish washing liquid 1/2 a tablespoon of salt 2/3 cup water |
Safety ProceduresMaterial 1: Disposable gloves
Material 2: Lab coats Although are materials are not hazardous the gloves and coat help us to not get stains on our clothes. |
ProcedureRemove green top from strawberry and place it in a zip-loc bag. Press the air out of the bag and seal it. Mash the strawberry for 2 minutes to break open the cell walls. Add 10 ml of DNA extraction buffer to the bag.Press the air out and seal the bag. Mash the bagged strawberry with the buffer for 1 minute. This will help dissolve the membranes of the cell nuclei and release the DNA. Filter the liquid into the test tube by passing it through the cheese cloth or coffee filter in the funnel. This will separate out the undissolved parts of the strawberry. Do not fill the test tube more than 1/4 full. Add the ice cold isopropyl alcohol to test tube by letting it slowly run down the side of the tube so that the alcohol will form a layer on top of the water/strawberry solution. Dip the glass rod or plastic loop into the test tube until it reaches the point where the alcohol and water solutions meet. Twirl the rod to let the DNA strands collect on it.
Special Needs: For our experiment, we will be bringing a cooler of ice and a large bottle of water. We will be providing all materials which include Isopropyl Alcohol. |
The Science behind it
The DNA strands from the strawberry will collect on the rod. They may look like fine white threads. While these may look like individual strands of DNA, single strands would be too small for us to see. They are actually bundles of DNA molecules (and they may include some protein - another polymer - too). So -how are we getting the DNA out of strawberries? Well, when we mash the strawberry we are breaking the walls of individual cells of the strawberries. The contents of those cells leak out and form the red liquid in the bag. But, the DNA is not loose and in the fluid of the cells- it is in the nucleus of each cell. It was funny when we mashed up the strawberries in a bag because if felt squishy and gooey. In the end, we were surprised by how brittled the DNA was.
Reference: Taken from "Polymer Science for the Elementary School Classroom by Catherine Chess, Laura Kosbar and Sharon Nunes,Thomas J. Watson Research Center, Yorktown Heights, NY.
Reference: Taken from "Polymer Science for the Elementary School Classroom by Catherine Chess, Laura Kosbar and Sharon Nunes,Thomas J. Watson Research Center, Yorktown Heights, NY.
Conclusions
We thought that the DNA would be red because of the outside of a strawberry. But the DNA is inside the cells and that DNA turned out to be white. The color of the DNA is not necessarily the color of the object. We were also half right because the DNA is long according to the size of the strawberry.