Strawberry DNA Extraction Lab

Friday, February 1, 2013

      Today, I along with my lab partner, took part in a lab to extract the DNA from just an ordinary strawberry. In this post, I will go over each of the steps of the lab and how is affects the strawberry.

Materials:
     Zip lock plastic bag
     1 Strawberry
     10mL DNA extraction buffer
     Gauze cut into squares
     Funnel
     Ice cold ethanol
     Plastic transfer pipette
     Clear test tube
 
Step 1: Create DNA Extraction Buffer:Makes 50mL (enough for 5 extractions)
  Materials
     5mL liquid dish washing detergent or shampoo
     .75g salt
     45mL water
   Measure detergent and water into a measuring cylinder, weigh out the salt and combine ingredients into a bottle or beaker.

Step 2: Wash strawberry, remove the leaves, and put into the zip-lock bag. Add in 10mL of the extraction buffer into the zip-lock bag. After making sure all air bubbles are gone, seal the bag and crush the strawberry for about 1 minute. NOTE: Do not crush the strawberry for too much for it will cause the DNA to degrade.

Crushing the strawberries with the extraction buffer.

   What is Happening?
     Crushing the strawberries breaks open the strawberry cells which exposes the nuclei, where the DNA is stored. The detergent contained in the buffer mixture break down the the phospholipid membrane of the nucleus which releases the DNA. Because the DNA strands will repel each other, the sodium ions of the salt will neutralize the charge and even attract each other. This will result in the DNA to clump together.

Step 3: Place funnel lined with gauze into the test tube.

Step 4: Pour the strawberry DNA extraction buffer mixture into the gauze and filter the mixture into the tube through the gauze.

Filtering the strawberry pulp.

  Why Do This?
     This only filters out all of the debris, including cell walls. The DNA is dissolved in the extraction buffer and will pass through.
Step 5: Keep the liquid filtered into the tube and discard the gauze and the strawberry pulp.

Here is the strawberry extract.

Step 6: Layer an equal volume of ice-cold ethanol on top of the strawberry solution in the test tube using the plastic pipette. Note: The ethanol must be cold. The if it is too warm, the heat energy will denature, or break apart, the DNA strands.
  What Are You Seeing?

This is how the final product should turn out.

     The DNA should collect between the layer of alcohol on top and the strawberry extract on the bottom. The DNA should collect and form into long mucus-looking strands.