DNA is found in cells from
Animals and Plants. DNA is a double stranded macromolecule composed of
nucleotide bases pairing Adenine with Thymine and Guanine with Cytosine.
DNA can be extracted from cells by a simple technique with household chemicals,
enabling students to see strands of DNA with the naked eye.
To extract DNA from the fruit
of a strawberry plant
/ Equipment (per student group):
1. heavy duty
(fresh or frozen and thawed)
100 ml beaker
7. wooden coffee stirrer
Extraction Buffer (One liter: mix
100 ml of shampoo (without conditioner), 15 g NaCl,
900 ml water OR 50 ml liquid
dishwashing detergent, 15 g NaCl and 950 ml water)
ethanol or 95% isopropyl alcohol
strawberry in a zip lock baggie and carefully press out all of the air and seal
strawberry with your fist for 2 minutes.
Add 10 ml
extraction buffer to the bag and carefully press out all of the air and seal the
Mush again for
cheesecloth in a funnel into beaker. Support the test tube in a test tube rack.
extra mashed strawberry.
into test tube so that it is 1/8 full.
the ice-cold alcohol into the tube until the tube is half full and forms a layer
over the top of the strawberry extract.
interface, you will see the DNA precipitate out of solution and float to the
top. You may spool the DNA on your glass rod or pipette tip.
Spool the DNA by dipping a pipette tip or glass rod into the tube
right where the extract layer & alcohol are in contact with each other. With
your tube at eye level, twirl the rod & watch as DNA strands collect.
Take a look at the sketch of the plant cell below.
The chromosomes (which are made of DNA) are in the nucleus. This is the only
place where DNA is located.
Now match the procedure with what it is doing to help isolate the DNA from the
other materials in the cell.
_____1. Break open the cell
A. Squish the fruit to a slush
_____2. Dissolve cell membranes
B. Filter your extract through cheesecloth
Precipitate the DNA (clump the DNA together
Mix in a detergent solution
Separate organelles, broken cell wall, and
membranes from proteins, carbohydrates, and DNA
Layer cold alcohol over the extract
DNA Extraction Table
AMOUNT ADDED OR OBTAINED
SKETCH OF TEST TUBE WITH CONTENTS
Where can DNA
be found in the cell?
action of the soap (detergent) on the cell. What is the purpose of the
soap in this activity?
What was the
purpose of the Sodium Chloride? Include a discussion of polarity and charged
Why was the
cold ethanol added to the soap and salt mixture?
appearance of your final product?
Draw a diagram
of DNA containing 5 sets of nucleotide bases labeling the hydrogen bonds
between the bases.