Investigating DNA extraction

Dave Hassan of Columbus Grove High School shares about a new approach to a DNA extraction lab:

My freshman science class performed the DNA extraction lab which we did in the Science of Food and Fuel workshop this past summer. After lessons involving the structure of cells and the structure and function of the DNA in those cells, we discussed the steps that would be necessary to actually see the genetic material in a cell.

Thinking through what it would take to actually open the cells, remove, and uncoil the DNA, the students set about developing a process that they believed could work. In my opinion, better than actually seeing the end product (extracted DNA), they were challenged to think about the chemicals/structures they had to deal with and overcome to actually even get to the genetic material.

Students offered ideas including chopping, crushing, and grinding cells to break them open, but after discussing the effect plain old dish soap could have on the cell membrane, all opted to use the Palmolive soap included in the supplies. As some of the students settled in on processes that they really believed would be effective, I had others that remained skeptical that seeing DNA was even possible. Using slightly different processes it was interesting to watch as each group had some level of success pulling various amounts of DNA out of their samples. The students that were confident in their processes felt validated that it worked. The skeptical students grinned as they saw the DNA come out of the solution when they added the rubbing alcohol.

As a teacher, sometimes it is easy to forget the fact that a lab like this DNA extraction can really grab the interest of your students, and often for different reasons. Students whose goal it was to “get the most DNA” learned that for very good reasons, slight variations in their procedure could significantly affect the outcome. Others gained appreciation for the fact that we could think through the process and come up with a procedure that allowed fourteen year old kids to get at, and see, the stuff that fundamentally makes them up.

As my students left that day there was a lot of chatter—including words like “cool” and “impressed”—about what they had done. Not a bad day in the science lab when students leave having that kind of discussion!