Strawberry DNA Extraction Laboratory
Materials:
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1 heavy zip-lock baggie
1 thawed strawberry
cheesecloth
funnel
100 ml beaker
test tube
glass stir
DNA extraction buffer
Ice-cold 95% ethanol
Safety goggles
Procedure:
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Place one strawberry in a zip-lock baggie.
Smash strawberry with fist for 2 minutes
Add 10 ml extraction buffer to the bag.
Mush again for one minute
Filter through cheesecloth in a funnel into beaker.
Pour filtrate into test tube so that it is 1/8 full.
Slowly pour the ice-cold alcohol into the tube until the tube is half full.
At the interface, you will see the DNA precipitate out of solution and float to the
top. You may spool the DNA on your glass rod.
Questions:
1. Where can DNA be found in the cell?
2. Discuss the action of soap (detergent) on the cell. What is the purpose of the soap
in the activity?
3. What was the purpose of the Sodium Chloride, include a discussion of polarity
and charged particles?
4. Why was the cold ethanol added to the soap and salt mixture?
5. Describe the appearance of your final product?
6. Draw a diagram of DNA containing 5 sets of nucleotide bases labeling the
hydrogen bonds between the bases
Answer:
The liquid detergent causes the cell membrane to break down and dissolves the
lipids and proteins of the cell by disrupting the bonds that hold the cell
membrane together. The detergent causes lipids and proteins to precipitate out
of the solution. NaCI enables nucleic acids to precipitate out of an alcohol
solution because it shields the negative phosphate end of DNA, causing them to
come closer together and coalesce.
The DNA does not dissolve in alcohol and therefore forms a precipitate (solid)
layer where it contacts the cold alcohol. This separates the DNA from other
macromolecules and from the cell contents.
Buffer Solution Prep:
950 ml of water, 50 ml of dish detergent, and 15 g of NaCl