Laboratory: Strawberry DNA Extraction
Introduction
Scientists often have to collect DNA from organisms to find out what kinds of genes the creature uses. Here's a really simple protocol (procedure) to get DNA from a strawberry using only alcohol, water, dish detergent and salt!
DNA Extraction Pre-lab
1. What does DNA stand for?
2. Label the 6 parts of the DNA molecule.
3. What do the letters stand for in the picture?
A =
T =
G =
C =
P =
4. DNA extraction is the process of taking out the DNA from the nucleus and cell. Do you think the DNA from a human and a strawberry would look the same or different from each other? Explain your reasoning.
5. For the experiment to work, you have to add dishwasher detergent to the strawberry. The detergent helps to break down fat. Why might this be necessary for the experiment to work?
Materials (per group):
1 medium-sized strawberry Ice
1 clean cheesecloth DNA Extraction Buffer
1 funnel (NaCl, H2O, Palmolive dishwashing liquid)
1 test tube (20 x 200cm) isopropanol alcohol (keep in the hood)
1 Ziploc bag 1 test tube rack
1 wooden toothpick
Procedures (COPY)
1) Place the cheesecloth in the funnel provided. Place the funnel in the neck of the test tube. Leave the wooden stick on the table for now.
2) I have put together the DNA extraction buffer already (water, salt, detergent)
3) Place one strawberry in your Ziploc bag. Add 5ml of extraction buffer and close the Ziploc bag well. (Try to let out all the air)
4) Smoosh and smash the strawberry around until no big chunky parts remain. Let the bag sit on your table for 3-5 minutes. The DNA will be ready for extraction by then.
5) Draw a picture of your bag of extraction mixture hereà
Describe any particulars: color, consistency, etc.
6) Filter by pouring the juice through the cheesecloth into the test tube. You might have to help push some through with your fingers. Don't worry if a few chunks get through.
7) While holding the test tube at an angle (tilt), carefully and slowly drip 5ml of ice-cold Isopropanol (alcohol) down the side of the test tube so it does not mix with the strawberry liquid.
8) Draw what you see in the test tube. Identify and label the layers à
Be sure to note color, relative volume, and thickness of materials in each layer.
9) Use the wooden toothpick to try to lift the DNA from the tube.
10) Describe what you see as you try to lift the DNA out of the tube. (observations)
11) What does it look like?
Is it easy to grab?
Describe the color and consistency.
12) Return your supplies to the proper area, clean and begin on the questions below.
Conclusion Questions
1) What is the purpose of using the extraction buffer? (Why is dishwashing soap used? Why is salt used?)
2) What is the purpose of smashing the strawberry into mush?
3) What is the purpose of using the cheesecloth?
4) What is the purpose of using the isopropyl alcohol?
5) What layer did you find the DNA in and why was it in that layer?