Yeast DNA Extraction

DNA is a nucleic acid located in the cell's nucleus. It is found making up the genetic material and is bound to several types of proteins. The nuclear and the cell membranes are a tough protective barrier, made of lipids and proteins, which need to be eliminated in order to release the DNA. It is very important that the directions be followed carefully to ensure good results.


Materials
dry yeast Adolph's natural meat tenderizer
beaker distilled water
non-iodized salt glass stirring rod
Palmolive detergent graduated cylinders (10ml and 100ml)
blender 15 ml test tube
ice cold 95% ethanol test tube rack
phenol red indicator


Solutions
detergent/salt solution: 20 ml detergent
20 g non-iodized salt
180 ml distilled water
5% meat tenderizer solution: 5 g tenderizer
95 ml distilled water

Protocol
1. Mix 1 package of dry yeast with 40 mL of 50oC tap water to dissolve the yeast in a beaker. Keep mixture covered and warm for about 20 minutes.
2. Add 40 ml detergent/salt solution.
3. Place mixture in a blender and blend 30 sec-1 minute on high.
4. Pour mixture back into the beaker, add 15 ml of meat tenderizer solution, and stir to mix.
5. Place 6 ml of mixture into a test tube.
6. Carefully pour 6 ml of ice cold ethanol carefully down the side of the tube to form a layer.
7. Let the mixture sit undisturbed 2-3 minutes until bubbling stops.
8. You will see a precipitate in the alcohol. The precipitate is DNA. Using a twirling motion, slowly move the scored end of a glass rod through the interface of the alcohol/aqueous layers. Collect the mucus-like DNA and place it in a test tube containing 5% salt solution.
9. Test for the presence of DNA in your extraction and in the centrifugation pellet with 4-5 drops phenol red.


Questions to be addressed in the discussion
1. What steps were undertaken to eliminate any protein contamination in the extraction?
2. Why was phenol red used to test for the presence of DNA?
3. What was used to disrupt the membranes of the cell and nucleus? (think about this one)
4 In a cell, DNA is wrapped around proteins (called histones) like thread on a spool. Knowing this, why is salt added to our solutions?