Workshop Plans: DNA Extraction

Next month, I'm doing a workshop for a small Catholic school in WV.  I like to promote inquiry-based instruction. One of the workshop topics is DNA Extraction Lab.  Yes, you can follow the directions as written and perform a decent lab.  Why not make it more inquiry-based?  Let's look at the materials: split peas, salt, alcohol, meat tenderizer, and liquid detergent.  (I know from experience it pays to buy the meat tenderizer fresh.)  I instruct my students to do the DNA extraction according to the instructions.  Then, I ask them to try either different alcohols (or concentrations of alcohols), different detergents, or types of salts.  The kids end up repeating the same basic experiment several times.  The results are determined by the amount of DNA produces.  It's important to vary one factor at a time.  Otherwise, how will you know which factor improved or diminished the results?  Be sure to have the kids record their experiments explaining which factor they changed.  Check to see they keep the measures the same.  Use photos to compare the amount of DNA extracted.