DNA Extraction Lab / Name ______
Date ______
Essential Questions
1. Where is DNA found? / Vocabulary
DNA, chromosomes, solution, extraction, solvent, precipitation
/ Objectives
1. Recognize that DNA is a part of organic matter.
Materials:
2 Frozen Strawberries (allow to come to room temperature)
Quart size freezer Ziploc bag
Coffee filter
Coffee stirrers (flat wooden) or loop tool
Cups, or flask, 15ml centrifuge tubes
Extraction buffer (100 ml dishwashing liquid, 900 ml distilled water and 15 grams NaCl/salt.)
Ethanol
Optional: DNA
Why’s:
Strawberries? 8 times the amount of DNA of normal cells
Why frozen? Ice disrupts cells.
Detergent? To disrupt cell membranes to liberate (release) the DNA
Salt? To shield the negative charges on DNA to allow precipitation
Alcohol? To cause DNA to precipitate
Super Scientist Vocabulary Alert: Please try to use the following academic science vocabulary words in your conversation and in your writing while conducting this investigation!
DNA chromosomes extract solution soluble precipitate
Procedures:
1. Place 2 strawberries in the plastic bag. Remove air and seal.
2. Mash strawberry for 2 minutes.
3. Add about 10 ml DNA Extraction buffer. Remove air and seal.
4. Mash for 2 more minutes.
5. Pour solution through coffee filterinto a cup or beaker.
6. Pour about 2 ml of this solution back into the 15 ml tube. It will be very red. The DNA is now suspended in the liquid, but you cannot see it yet.
7. Rinse your graduated cylinder before you complete the next step.
8. Very slowly pour about 4 ml of cold ethanol so that it lies on top of the strawberry solution. OBSERVE.
9. If the tube just sits, there will be DNA where the strawberry solution and the ethanol meet with bubbles in it. If you gently rock the tube, more DNA will come out of solution and eventually float to the top. OBSERVE.
10. Once you see white, stringy clumps of DNA, use your coffee stirrer or loop tool to extract a clump of DNA from the test tube for closer observation. Use the hand lens to examine the DNA more closely.
POST LAB QUESTIONS
Please answer the questions in complete sentences in your journal.
Regular Science Post Lab Questions:
1. Describe the appearance of the DNA you extracted and draw a picture of the DNA sample. Is it what you expected?
2. Where is DNA in a cell? Explain what we had to do in the lab to “get to” the DNA?
3. Compare the DNA you extracted from the strawberries to the model of DNA that we made in class. Similarities? Differences?
4. A person cannot see one strand of cotton thread 100 feet away, but if you wound thousands of threads together into a rope, it would be visible much further away. How does this statement relate to our DNA extraction? Explain.
Pre AP Science Post Lab Questions:
1. Compare the DNA you extracted from the strawberries to the model of DNA that we made in class. Similarities? Differences? Is it what you expected?
2. Explain the role of the DNA extraction buffer (dish soap and salt) and the alcohol in the DNA extraction process. Draw pictures if that helps.
3. A person cannot see one strand of cotton thread 100 feet away, but if you wound thousands of threads together into a rope, it would be visible much further away. How does this statement relate to our DNA extraction? Explain.
4. Analyze the lab procedure. How do you think this lab would be different if you were trying to extract DNA from a human?