Mrs. Pfahnl’s Bio A Lab DNA Extraction
Purpose: Extract DNA from fruits at home.
4. One new ziplock bag (sandwich or freezer bag)
keep it in freezer before starting the experiment
7. Clean transparent glass cup
8. Toothpick or fork
9. Clean measuring tools (spoons and cups)
Or 4-5 strawberries without stems
Or a kiwi without skin
1. Add detergent, salt and water into a ziplock bag and mix well
2. Add fruits into the bag, let out as much air as possible, lay flat on counter and smash into small pieces with fingers
3. Use strainer to filter out the fibers and leave liquid mixture in a cup (about a cup). If cheesecloth or paper towels is used, volume may be less.
4. Measure half cup of the mixture liquid (from step 3)
5. Measure ⅛ to ¼ cup freezer cold antiseptic alcohol or half cup of triple distilled Voldka
6. Pour the cold alcohol (from step 5) along the side of the cup to create a clear layer on top of the liquid (step 4)
7. Do not disturb. Wait and observe for a few minutes.
8. Use toothpick to fish out DNA strands
1.The function of salt is to distrupt the structure of plant cell wall, so it becomes permeable for detergent to have contact with cell membrame.
2. The function of detergent is to disove cell membrane and nuclear envolop to release DNA from the nucleus.
3. Filtration by strainer is to separate cell wall and DNA mixture.
4. DNA is not soluable in cold and high concentration of cold alcohol.
5. Alcohol is lighter than water. Thus, the cold alcohol will float on top of the DNA mixture in step 6. However, alcohol is soluable in water, pouring alcohol slowly along the edge of the cup is necessary to prevent it from mixing with water.
6. DNA in mixture of step 4 enters alcohol layer of step 6 through difusion process. DNA will appear in the alcohol layer due to precipitaion.
7. Plant genomic DNA strands are very long. After enough DNA precipitated in the alcohol layer, the long strands may tangle together and easily be picked out.
8. Overall, this is a fun experiment for students to learn and understand DNA.