What is DNA? DNA Extraction from Kiwifruit

Adapted from the Office of Biotechnology, Iowa State University

Introduction

DNA is present in the cells of all living organisms. This procedure is designed to extract DNA from kiwi in sufficient quantity to be seen and spooled. This activity is ideal for students to work in pairs, but each student will have a tube of DNA at the end.

Some questions to get you thinking about today's lab:

1. One way to purify a molecule is to get rid of everything but that molecule. If we want to isolate DNA from kiwifruit, what do we have to get rid of?

2. What materials would you use to do that?

3. What can we do with the DNA once we've purified it?

   Materials

   • ziplock bags
   • jar or beaker that fits strainer or funnel strainer or funnel
   • cheese cloth (cut to cover the funnel)
   • ice water bath (a large mixing bowl works well)
   • extraction solution
   • kiwifruit
   • cold 95% ethanol or isopropanol
   • small test tubes (1 per student)

   Protocol

   1. Get 4 pieces of kiwi and put them in a ziplock bag.
   2. Add 20 ml of extraction solution to the ziplock bag. Make sure the bag is closed without much extra air. Mush the kiwi thoroughly but carefully so the bag doesnŐt break, for about 5 minutes. What does mushing the kiwi do?

   3. What do you think the extraction solution is? What does it do to the kiwi?

   4. Cool the kiwi mixture in the ice bath for a minute. Then mush the kiwi more. Cool, then mush. Repeat this several times. Why do we cool the mixture?

   5. Filter the mixture through the cheesecloth. All the groups can combine their mixtures at this point, to filter together. What is being filtered out? What is going through the filter?

   6. Dispense approximately 2 ml of kiwi solution into each test tube, one for each student.

   7. Being careful not to shake the tubes, add approximately 2 ml of cold 95% ethanol to each tube. What do you think the ethanol does? Why do we want it cold?

   8. Take a look at your tube. What do you see in the top portion of the liquid?

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      BIOTECH Project Department of Molecular and Cellular Biology The University of Arizona September 14, 2000 Designed by: Erin Dolan Nadja Anderson, Ph.D. nadja@email.arizona.edu http://biotech.biology.arizona.edu