DNA Extraction Lab

DNA Extraction Lab

          In this lab, we asked the question, "Can DNA be extracted from cheek cells, and if so, at what point do you predict you will be able to see the DNA?" To answer this, I said yes, DNA can be extracted from cheek cells because our skin cells have our DNA in them. We found that we would be able to see the DNA after adding the detergent, salt, and pineapple juice to the gatorade mixture and after carefully placing alcohol on top of it. The DNA fell out of the solution as the alcohol was added because the alcohol is nonpolar and the DNA is polar. My hypothesis was "If DNA is in our skin cells, then we will be able to separate DNA from our cheek cells." 

        One of the errors we encountered in this lab was an issue with the lids falling inside of the test tube, rather than closing the test tube. Because of this, we weren't able to effectively shake the mixture we had created with the gatorade, salt, detergent, and pineapple juice. One recommendation I have for anyone conducting this experiment is to be sure to use a cap that fits the right test tube, otherwise, the experiment will most likely turn out wrong for that person. 

       The DNA extraction protocol involved three steps: homogenization, lysis, and precipitation. We used the gatorade to homogenize the cell tissue in our cheeks. We then added soap to lyse the cell membranes and to emulsify the lipids and proteins of the cell. This disrupts the polar interactions that hold the cell membrane together. We then added pineapple juice as a catabolic protease to further break down any proteins called histones that the DNA molecule wraps itself around. 95% isopropanol alcohol was then layered on top of the mixture. Since the alcohol is nonpolar and the DNA is polar, the DNA falls out of the solution as a precipitate right at the interface of the two solutions. The DNA can then be pulled up from the alcohol layer and then collected with a transfer pipette. This lab was important in understanding biological concepts by demonstrating what it means to homogenize a mixture, and what lysis and precipitation mean.