Name: _______________________ Per: ____
Background Information: Every organism has DNA. The science of genetic engineering involves intentionally changing an organisms DNA to produce a desired result. In order to manipulate the DNA, it must first be extracted from the organism’s cells. Not only is DNA extraction useful for genetic engineering, it is also useful to help learn more about humans and other living things. Humans don’t look much like a fly or a worm, but we share genes with both of them—and with every other living organism. By studying the extracted DNA of other organisms, scientists learn important information about the human genome.
Pre-lab questions
1. Remember that genes are large segments of DNA, and genes control traits. Give two examples of traits you would look for in a strawberry that you wanted to eat.
________________________________________ and ________________________________________________
2. It is impossible to see an individual strand of DNA without a microscope. However, if a bunch of strands are clumped together, they are visible to the naked eye. Using the sentence frame, make a prediction of what you think the strawberry DNA will look like. I think the DNA will look _____________________________________________________.
Purpose: To extract DNA from strawberries and examine DNA superstructure.
Procedure
1. Place the piece of strawberry inside the zip lock bag, closed with no air inside.
2. Squeeze or knead the bag for 1 minute. Try to get the strawberry mostly liquid with few or no “chunks.”
3. Add 5 ml of DNA Extraction Buffer (soapy water) and continue to knead the mixture for 2 minutes.
4. Carefully pour SOME of the strawberry mixture from the bag into the test tube. There should be enough liquid for both pairs at the table.
5. Slowly pour 10 ml of ethanol down the side of the tube so that it forms a separate layer on top of the strawberry liquid. Keep the test tube upright and do not mix the contents!
6. Watch the material for about 1 minute. When you see a fluffy white cloud form at the interface between the two liquids, use the paper clip to collect it. This is the DNA!
7. Gently spool the DNA onto the paperclip and transfer the material to a piece of paper towel. Examine the texture of the DNA carefully.
8. Throw away the paper towel. Keep the Ziploc bag and paper clip to be used again.
Analysis Questions
Matching: Match the procedural step to the purpose it served in the lab experiment.
___1. Placing the strawberry inside of a Ziploc bag A. To dismantle proteins and dissolve cell membranes
___2. Initial smashing and grinding of strawberry
___3. Adding the extraction buffer to the strawberry
___4. Addition ethanol to the strawberry solution
B. To separate the DNA from the rest of the solution
C. To contain the strawberry and prevent mess
D. To break open the cells

5. Why does the DNA extraction buffer contain dish soap? Use a complete sentence to defend your answer. Hint: Cell membranes are a lipid (like fats and oils.) _________________________________________________________________
___________________________________________________________________________________________________.
6. Using a complete sentence, describe what happened to the strawberry solution when you added the ethanol. ______
___________________________________________________________________________________________________.
7. Using a complete sentence, describe what the DNA looked like. ____________________________________________
___________________________________________________________________________________________________.
6. A person cannot see a single cotton thread from 100 feet away. But if you wound thousands of threads together into a rope, it would be visible at the same distance. Evaluate how this statement is an analogy to our DNA extraction? ___
___________________________________________________________________________________________________.
7. Why is the ability to extract DNA from an organism’s cells useful for scientists? List two reasons.
1. _____________________________________________________________.
2. ____________________________________________________________.
8. Remember that creating transgenic organisms is a type of genetic engineering. A transgenic organism is a living thing that has been modified with the genetic material from another species. Suppose you are asked to create a transgenic strawberry. What type of DNA do you think would be useful to insert into the genome of a strawberry?
Defend your answer using at least two complete sentences.
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Think Pair Share: Please wait for your instructor to give you directions.
Question What I Think What My Partner Thinks