<p> IHS / Biology</p><p>DNA Spooling from Strawberries! Adapted from: The GENETICS Project, Department of Genome Sciences, UW, 2012</p><p>Background In this activity you will extract or "spool" DNA -- genetic material -- from plant cells. While all organisms contain DNA, some make better sources for spooling than others. Strawberries are a good choice as their genome is octoploid, meaning they have 8 copies (!) of each chromosome (we humans are diploid – we have 2 copies of each chromosome per cell). Most of the unusual physical properties of DNA result from it being a very long, thin molecule. Each of your cells, for example, contains approximately two meters (six feet) of very thin, compact DNA!</p><p>Purpose: To isolate DNA from the cells of strawberries, and wind it up on a stir stick (“spooling”)</p><p>Materials strawberries (fresh or frozen, about 1-2 per student) funnel sealable plastic bag (preferably freezer quality) test tube in test tube rack extraction buffer graduated cylinder</p><p>(50 ml dishwashing detergent, 2 tsp. non-iodized salt, fill to 1 L with H2O) glass stirring rod cheesecloth (or loosely woven unbleached muslin) 95% ethanol, chilled </p><p>Procedure • HINT Any molecule as long as DNA is vulnerable to cutting by enzymes on your skin called DNases. So use only scrupulously-clean glassware or plastic, and don't touch anything that is going to go into your solutions.</p><p>1. Remove the green sepals from the strawberry.</p><p>2. Place the strawberry into the plastic bag, push out as much air as possible, and seal shut.</p><p>3. Squish the bag for a few minutes to completely squash the fruit.</p><p>4. Add 10 mL of extraction buffer (soapy salty water) to the bag and squish for a few more minutes. Minimize the amount of soap bubbles.</p><p>5. Filter the strawberry mixture by carefully pouring it through a funnel lined with cheesecloth into a test tube. If chunks of strawberry remain, filter a second time. The pink filtrate contains DNA released from the strawberry cells.</p><p>6. Perform the next step VERY CAREFULLY! Add approximately 2 volumes of ice-cold ethanol to the strawberry liquid in the test tube. As you do this, pour the ethanol SLOWLY down the side of the test tube so that it forms a separate layer on top of the strawberry liquid. DO NOT MIX!!</p><p>7. Let the tube sit undisturbed for 1-2 minutes.</p><p>8. It's time to see if you have extracted strawberry DNA -- so let's spool! Slide a long, thin, clean glass rod into your tube until it penetrates the interface between the less polar ethanol layer (top) and the hydrophilic pink layer (bottom). Then, begin making a circular, stirring motion with it, as if you’re stirring a witch’s brew! </p><p>9. If you are successful, long threads of DNA will precipitate onto the glass rod! "Reel in" a good-sized clump of fibers! These are not single DNA molecules, but huge ropes of thousands of molecules twisted together. </p><p>10. If you’d like to save your strawberry’s DNA, ask your teacher how to do so!</p><p>Upon completion of this activity: • Dispose of the used baggie and cheesecloth into the trash. Pour the liquid down the sink. IHS / Biology</p><p>• Leave equipment as you found it, and check that your work station is in order. • Wash your hands.</p>