Isolation of Banana DNA

Title: Isolation of Banana DNA

Approximate Running Time of Exercise: 1-1.5 hours Purpose: This laboratory exercise is perfect for those who do not have direct access to biotechnology laboratories and specific materials related to DNA isolation. The general purpose of this laboratory exercise is to utilize common household ingredients to extract the DNA from a banana out onto a glass rod or toothpick. This exercise allows students to witness the biotechnological phenomenon as the DNA from a banana slowly extracts itself and rises to the surface of its medium. Coupled with the class exercise on constructing a basic DNA molecule out of simple materials that accompanies the lesson on DNA structure and function, this laboratory exercise expands upon the students’ knowledge of the fragility and seemingly infinitesimal size of DNA. THIS LAB WILL BE DONE IN GROUPS OF TWO!!!

Safety: To ensure safety of all participants, this laboratory exercise should be conducted under the supervision of your teaching assistant. Safety goggles are required [as always!] due to the nature of the materials being used, and use caution when handling the rubbing alcohol and hot water.

Objectives: Upon completion of this laboratory exercise, students will be able to:

Develop proper safety and handling techniques to mimic future work in a biotechnology laboratory

Use standard biotechnology laboratory equipment and materials

Prepare samples of DNA from bananas

Observe a sample of DNA and note its fragility

Isolation of Banana DNA

Background Information/Overview:

Need more information for this (about why the ingredients that are used do the things that they do)

Include scanned-in pictures of the actual outcome (to be done later) Materials: To be able to complete this exercise, you will need the following items:

1. Access to a freezer (for pieces of ice and ice-cold alcohol) 2. One bucket (big enough to hold a bottle of rubbing alcohol) per group of students (5

per group) 3. Ice (enough to partially fill the bottom of each bucket) 4. 2 bananas (½ banana per group)

5. 40 mL of Woolite brand detergent (10 mL per group) 6. 2 teaspoons table salt (NaCl) (½ teaspoon per group) 7. 360 mL water (90 mL per group) for the soap/salt solution 8. 4 100mL-beakers, or 4 small, clear, plastic cups (one per group) 9. Hot water bath (each group may use this-will require a hot plate) 10. Plastic thermometer 11. Ice water bath (each group may use this-will require extra ice and more water) 12. 8 pieces of cheesecloth (2 per group) 13. 4 small funnels (one per group) 14. 4 test tubes (one per group) 15. 36 mL of ice-cold rubbing alcohol (9 mL of 91% isopropyl alcohol per group) 16. 4 tubes or small cups (one per group to hold the isopropyl alcohol) 17. 4 long toothpicks or clear glass stirring rods (one per group); the glass rods make the

DNA easier to see towards the end of the laboratory exercise 18. A blender (one per group, or just one will do if each group shares) 19. 4 plastic teaspoons (one per group) 20. 4 large pieces of parafilm (one piece per group) 21. 4 measuring cups with mL marks (one per group)

Approach/Procedure: *Note: Make sure to keep the rubbing alcohol as cold as possible (store it in the freezer and then keep it in an ice bucket during the laboratory exercise).

Read through this entire procedure. Before you begin, predict the appearance of the DNA and write this on your laboratory note sheet.

Obtain one bucket per group, and line the bucket with ice cubes. Place the 9 mL of isopropyl alcohol within the bucket, and make sure to keep the alcohol submerged within the ice to keep it as cold as possible.

Isolation of Banana DNA

Make the soap/salt solution:

o Carefully blend 10 mL of Woolite brand detergent, ½ teaspoon of NaCl (table salt), and 90 mL of water in a blender on high speed (making sure the blender top is screwed on tightly to avoid a potential mess!).

o Pour this soap/salt solution into a beaker, and place the beaker into a hot

water bath (at about 60C) for approximately 15 minutes. Any hotter than

60C will denature the DNA, and a period longer than 15 minutes will begin to break down the DNA.

After the 15-minute time period, put on the hand mitt and carefully remove the soap/salt solution from the hot water bath.

Blend the incubated soap/salt solution with ½ a banana on high speed.

Pour the banana mixture back into the beaker, and place the mixture in an ice water bath for 5 minutes to cool it down. This will slow any enzyme’s ability to break down the banana DNA.

After the 5-minute time period, carefully place 2 pieces of cheesecloth over a funnel placed in a beaker. This will filter the mixture and remove any un-pureed pieces of banana.

Place 6 mL of the banana filtrate into a test tube.

Immediately after this, tilt a test tube slightly and carefully pour 9 mL of ice-cold isopropyl alcohol down the inside of the slanted test tube. The tube is slanted here to reduce mixing of the alcohol and banana mixture.

Carefully hold the test tube to ensure no mixing of the 2 liquids, and begin to observe the formation of a clear layer of isopropyl alcohol atop the banana filtrate.

Allow the isopropyl alcohol to sit for 5 minutes without jarring the test tube. Bubbles will begin to form and rise up from the bottom of the test tube to the surface of the isopropyl alcohol. You will notice that the banana DNA will begin to rise and precipitate out of solution. The DNA will be a cloudy white color and is extremely fragile, so take care to avoid any sudden disturbance to the test tube.

Obtain a glass stirring rod or long toothpick, and gently place it into the test tube without disturbing the solution.

Carefully swivel the stirring rod or toothpick between your fingers and watch as the DNA wraps around the long surface. The DNA will look like white threads as it becomes secured to the stirring rod or toothpick.

References/Resources: Foresman, Scott and Addison Wesley. Biology: The Web of Life-Biotechnology Manual. Menlo Park, California: Addison Wesley Longman, Inc.,

Isolation of Banana DNA

THESE QUESTIONS AND THE ANSWERS SHALL BE TRANSCRIBED INTO YOUR NOTEBOOK

Isolation of Banana DNA

Prediction: __________________________________________________________________________________________________

Observations: Describe the characteristics of the extracted banana DNA, such as shape, texture, size, consistency, and texture (if you can determine this). If you have access to a microscope, record this, but if not, make your observations with the unaided eye.

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Analysis and Conclusions:

1. Before conducting this laboratory exercise, what did you think the banana DNA would look like? Did its appearance surprise you? Explain why or why not. ____________________________________________________________________________________________________________________________________________________________________________________________________

2. What other vegetables or fruits might be used for this lab? Why could these be used? ____________________________________________________________________________________________________________________________________________________________________________________________________

3. Name three properties of DNA that are demonstrated by this lab. How could you be certain that the substance you extracted from the banana/salt/soap/isopropanol solution was DNA? Explain your reasoning.

Isolation of Banana DNA

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POSTLAB QUESTION TO ANSWER What are some other techniques and methods that professional scientists use to extract and identify DNA from various organisms? What are your own thoughts on DNA research? Should we allow scientists to clone animals? Should we allow farmers to grow genetically altered foods?