Dna Isolation Lab Report

In brief, the purpose of this lab was to isolate DNA from a food sample, amplify the DNA using a polymerase chain reaction, and test the amplified DNA for the presence of the Bt gene or the 35s promoter. In part one of DNA isolation, the food sample was crushed before Lysis Buffer was added, in part to break down some cell walls, but also to increase area of the food sample being touched by the Lysis Buffer. The purpose of Lysis Buffer is to break down the cells in the food sample and release their DNA into the solution. By increasing the surface area to volume ratio of the food sample, this process is accelerated. After the initial Lysis Buffer addition, the mixture was further ground to increase the contact between the food sample and the
This is done so that 300 μl of supernatant can be transferred into a new tube without disturbing the debris. Next, isopropanol is added to the new tube in order to precipitate the DNA and make it settle. The tube is then centrifuged with the hinge of the tube facing upwards to pellet the DNA on the bottom of the tube under the hinge. This is done in this specific orientation so that if the DNA is too small to see, its location is still known. The supernatant is then removed without disturbing the pellet of DNA, and any remaining isopropanol is evaporated. This process is sped up by placing the tube in a heat block with the cap open. TE/RNase is then added to the tube of DNA. The side of the tube where the pellet is or should be is scraped with the pipette tip and the solution is pipetted up and down several times. This is done to facilitate resuspension. The TE buffer stabilizes the DNA, while the RNase destroys any isolated RNA that could interfere with the PCR reaction. The tube is briefly centrifuged once more in order to pellet any particles that remain undissolved. The tube of isolated DNA is kept on ice because it could contain nucleases that, at room temperature, could degrade the