Abstract
The purpose for this experiment was to explore the properties of Strawberry DNA. It was hypothesized that the DNA of a strawberry is red in color and soluble in ethanol. A Strawberry was placed in a self-sealing Zip Lock freezer bag from which air was removed. The bagged strawberry was mashed gently and 10 ml of extraction buffer was added. After further mashing of the bagged strawberry, the content of the bag was removed and filtered through cheesecloth into a test tube before adding alcohol. White clouds that resemble threads were seen floating on the surface of alcohol. These were the DNA. It was concluded that strawberry DNA is clear and insoluble in ethanol. This conclusion disapproved the hypothesis.
Introduction
DNA stands for deoxyribonucleic acid. It carries instructions that influence synthesis of various proteins in the body. Even though people think DNA is so small that it cannot be seen without a powerful microscope, experiments to extract and observe strawberry DNA show that it can be seen with naked eyes. DNA is double helix in shape and its structure is made of nitrogenous bases namely Guanine, Cytosine, Adenine, and Thymine (Burton, Zachary, and Kaguni, 354).
Grocery Store strawberries are suitable for this experiment for several reasons: they are good sources of DNA since they have 8 copies of each type of chromosome (This is called octoploid) (Bettelheim, Frederick, and Joseph Landesberg, 213), they are easy to mash, and ripe strawberries produce chemicals that help break down the cell membranes of strawberries hence facilitating the extraction of DNA.
Materials
Zip lock freezer bags
1 strawberry (fresh or frozen)
10 ml DNA extraction buffer (shampoo, salt & water)
Filtration Apparatus: cheesecloth or gauze, funnel and small beaker
Ice – cold ethanol (90% or higher concentration) in a dropper bottle
Large size test tubes
Glass rod or inoculating loop
Safety goggles
Lab apron
Sandwich bag
Method
The following procedure was followed in conducting the experiment: One strawberry was placed in a self-sealing zip-lock freezerbag. Air was pressed out of the bag and the bag then sealed. The bagged strawberry was then mashed gently with a fist and fingers for two minutes. Then, 10mL of extraction buffer was added to the bag. Air was pressed out of the bag again before it was resealed. The bagged strawberry with DNA extraction buffer was mashed further for about 1 minute while care was being taken to minimize bubbles.
Next, cheese cloth was placed into a funnel and the funnel placed at the mouth of a test tube. The bottom corner of the baggie was then cut off and the squished strawberry liquid squeezed into the filtration apparatus. It was allowed to drip into the test tube until the test tube was about 1/8 full. The funnel was removed and the cheesecloth discarded. Ice-cold ethanol was slowly drizzled from a dropper bottle along the side of the test tube until the test tube was almost half full such that it contained almost equal volumes of both alcohol and strawberry mixture.
A loop was then dipped into the tube up to exactly where the ethanol and extract layers were in contact with each other. Keeping the test tube at eye level, students observed precipitates of DNA and its characteristics noted.
Results
DNA precipitated out when ethanol was added. White threadlike clouds were initially seen at the point where layers of ethanol and strawberry mixture met and later on the surface of alcohol.
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Discussion
DNA is soluble in water but not in ethanol. This explains why precipitates of DNA were formed when alcohol was added. Water is a universal solvent. Strawberry DNA formed white precipitates hence implying that strawberry is white in color. DNA extraction buffer is made of soap, salt, and water. The shampoo used in this experiment is soap. It helps dissolve cell membrane and nuclear membranes. This helps release the DNA contained in the nucleus. On the other hand, salt helps prevent protein in the strawberry from mixing with DNA.
Conclusion
This experiment shows that Strawberry DNA is white and insoluble when ethanol is added. Therefore, the hypothesis was disapproved.
Works Cited
Bettelheim, Frederick A, and Joseph M. Landesberg. Laboratory Experiments for Introduction to General, Organic, and Biochemistry. Belmont, CA: Brooks/Cole, Cengage Learning, 2010. Print.
Burton, Zachary F, and Jon M. Kaguni. Experiments in Molecular Biology: Biochemical Applications. San Diego: Academic Press, 1997. Print.
