DNA Extraction
Procedure…
1. Place a strawberry in a Ziploc bag and squish with your hands for two minutes.
2. Add 3 drops of detergent, a pinch of salt, and 10 mL of water to the bag and
squish the contents with your hands for one minute more.
3. Add a pinch of meat tenderizer, and squeeze one minute.
4. Pour the strawberry mush through a funnel lined with a thin layer of cotton into a
beaker. Pour the strawberry solution from the baker into a test tube until the tube
is about half full.
5. SLOWLY trickle the cold alcohol down the side of the tube onto the solution in
the tube. The alcohol should form a layer on the surface of the solution in the
tube. Add cold alcohol until the tube in half full. Do not shake or mix the tube.
6. A white precipitate should start to appear at the interface of the solution and the
alcohol. This is DNA!
7. Use a wooden stick to pull up some of the DNA strands and examine them.
Squeezing… breaks up into individual cells
Detergent… Breaks apart the fat-based cell membranes, releasing the chromosomes.
Meat tenderizer… An enzyme that breaks proteins, in this case, the proteins that hold
DNA in the chromosome shape. Now the DNA is in long strands.
Salt… Adding salt (NaCl) to a solution containing DNA neutralizes the negative charges
of the DNA molecule, making the separate DNA molecules more likely to collect
together and become visible.
Alcohol… The DNA released from the cell nucleus is dissolved in the
water/detergent/specimen solution and cannot be seen. DNA precipitates out of solution
in alcohol, where it can be seen. In other words, DNA is less soluble in alcohol than in
water. When alcohol is added, the separate DNA molecules clump together and become
visible.
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