DNA IN MY FOOD???The Making of a SmoothiePrepared by the Office of Biotechnology, Iowa StateUniversity and then adapted by MosleyIn this protocol students will extract DNA from bananasthat have been blended with water. A portion of thebanana mixture is then treated with shampoo and salt,mixed for 5-10 minutes, and then strained through acoffee filter. The filtrate is added to cold alcohol and theDNA from the banana solution precipitates (becomesvisible). Materials: 2- 5 oz plastic cupsblenderplastic spoon for measuring and mixing#2 cone coffee filter20 ml of distilled waterclear-colored shampoo, such as Suave DailyClarifying Shampoo3- bananastable salt, either iodized or non-iodized1- plastic transfer pipette or medicine dropper1- sealed test tube containing 95% ethanol (grainalcohol) or 91% isopropyl (rubbing) alcohol1- container with ice for cold alcohol tubeslaboratory instructionsLab InstructionsExtract the DNADNA is present in the cells of all living organisms. Thisprocedure uses household equipment and store supplies toextract DNA from banana in sufficient quantity to be seenand spooled. The process of extracting DNA from a cell is the first stepfor many laboratory procedures in biotechnology. Thescientist must be able to separate DNA from the unwantedsubstances of the cell gently enough so that the DNA doesnot denature (break up. )You will prepare a solution of banana treated with salt,distilled water, and shampoo (detergent). The salt allowsthe DNA to precipitate out of a cold alcohol solution. Thedetergent breaks down the cell membrane by dissolvingthe lipids (fatty molecules) and proteins of the cell anddisrupting the bonds that hold the cell membrane together. The detergent then forms complexes with these lipids andproteins, allowing them to be filtered out of solution bythe coffee filter while leaving the cells’ DNA in thefiltrate. Procedure1. In a blender, mix a ratio of one banana per one cup(250ml) of distilled water. Blend for 15-20 seconds,until the solution is a mixture. (Your teacher isdoing this step for you )2. In one of the 5 oz cups, make a solution consisting of1 teaspoon of shampoo and two pinches of table salt. Add 20 ml (4 teaspoons) of distilled water or until thecup is 1/3 full. Dissolve the salt and shampoo bystirring slowly with the plastic spoon to avoidfoaming. 3. To the solution you made in step 2, add threeheaping teaspoons of the banana mixture from step1. Mix the solution with the spoon for 5-10 minutes. The salt enables the DNA strands to precipitate. )4. While one member of your group mixes the bananasolution, another member will place a #2 cone coffeefilter inside the second 5 oz plastic cup. Fold thecoffee filter’s edge around the cup so that the filterdoes not touch the bottom of the cup. 5. Filter the mixture by pouring it into the filter andletting the solution drain for several minutes untilthere is approximately 5 ml (covers the bottom of thecup) of filtrate to test. 6. Obtain a test tube of cold alcohol. 7. Fill the plastic pipette with banana solution and add itto the alcohol. (DNA is not soluble in alcohol. When alcohol isadded to the mixture, the components of the mixture,except for DNA, stay in solution while the DNAprecipitates out into the alcohol layer. )8. Let the solution sit for 2 to 3 minutes withoutdisturbing it. It is important not to shake the testtube. You can watch the white DNA precipitate outinto the alcohol layer. When good results areobtained, there will be enough DNA to spool on to aglass rod. Or by using a pasteur pipette that has beenheated at the tip to form a hook, you can retrievesome of the DNA. Conclusion Questions: 1. What is the subunit or monomer of the DNAstructure?2. What are the three parts of this subunit/monomer?3. Describe the appearance of the DNA you retrieved. 4. What is the role of the blender in this experiment?5. What is the role of the salt and the shampoo in thislab?6. Why were coffee filters (or cheesecloth) usedwithin this experiment?7. Why did you pour the solution with the DNA intothe alcohol?8. Why can’t we see the double helix shape of theDNA?
. What is the subunit or monomer of the DNA structure?
2. What are the three parts of this subunit/monomer?
3. Describe the appearance of the DNA you retrieved.
4. What is the role of the blender in this experiment?
5. What is the role of the salt and the shampoo in this lab?
6. Why were coffee filters (or cheesecloth) used within this experiment?
7. Why did you pour the solution with the DNA into the alcohol?
8. Why can’t we see the double helix shape of the DNA?