Apologia Biology: DNA Extraction Lab

Update: The last photo has a decent shot of the DNA.  It is white threads which float into the alcohol.

Update:  This week (after Thanksgiving) we're doing the DNA lab.  Yesterday's class went as expected.  The girls extracted mounds of DNA; the boys all need to try again.  See pix below.
Tomorrow, we're doing the DNA extraction lab with split peas--the instructions are in the Apologia textbooks.  (The first edition uses onions instead of split peas.  The link has directions for extracting DNA from just about anything.)  The key is to use fresh meat tenderizer.  My class is doing the lab as an inquiry project.  I bought three types of alcohol: denatured ethanol, and two different percentages of isopropyl or rubbing alcohol.  I also bought salt with and without iodine.  My materials include two brands of dish detergent, shampoo, and hand soap (clear).  The students will hypothesize which factor produces the most DNA.  (Remember, it's fresh meat tenderizer.)  The kids are going to test the different types of alcohol, salt, and detergent.  So, they'll do a number of trials.  I expect to take two class periods to do the lab; the kids will write another formal written lab report.  Here is my plan.

1.  Explain how to extract DNA and distribute lab instructions.  Our class will use 50 grams of split peas, 100 mL of cold water, two grams of salt, 15 mL of soap or detergent, and one gram of meat tenderizer.  The kids may need to adjust these measures.  I want the kids to weigh with a digital scale and measure volume with graduated cylinders instead of using cups and teaspoons, which are cooking measures.

2.  The next step is for each lab group to form a two-part hypothesis.  Here is an example.
    Null Hypothesis:  The type of detergent will have no effect on the amount of DNA produced.
    Alternative Hypothesis: Dawn dish soap will produce more DNA than Gain dish soap.

3.  Each group must identify controls and take note of the materials the group uses.

4.  Each group will perform at least three trials with different independent variables.  The groups chose which variable to test: alcohol, soap, or salt.


When I first did DNA extraction labs, I used expensive kits, chilled the alcohols,  used only ethanol, and timed each step precisely.  The kids may compare chilled alcohols to room-temperature alcohol.  This lab is usually a favorite.  I'll post pix this week.