Gel Electrophoresis

At the labs of the Wakehurst Place Botanical Gardens, I was given the chance to separate and identify DNA strands using a method known as gel electrophoresis. At Wakehurst, it is important that they can identify and recognise DNA from different species of plant, both to uphold the rules of CITES, an international initiative for the preservation of biodiversity, and to help with research and identification of their own specimens. Given the DNA samples of two types of timber, that the lumber companies claimed were cut in a particular forest approved by CITES, and a known sample from that certified forest, we were asked to determine if the two lumber samples had indeed come from the woodland they were supposed by be from.

First, I removed 20 micrometres of the known DNA sample from the sample given, using a very precise pipette designed specifically for this purpose. I then placed the sample in a small vial, already containing a naturally occurring enzyme called DNA helicase, that is used in the body to unzip DNA while transcription is taking place. The enzyme unzipped the antiparallel strands of nucleotides that form the DNA molecule and cut them into smaller pieces that we can use to identify where the DNA is from. Having given the mixture a firm shake to ensure that it is fully reacted, I stained the DNA to make sure I could see where it was during the electrophoresis segment of the procedure, that would follow.

We then submerged a piece of extremely even and well textured agar jelly into a buffer solution, which the DNA would move through in a process somewhat similar to chromatography. Injecting the DNA into a hole in the agar, and then running an electric current through the buffer caused the pieces of DNA to separate into identifiable bands. This happens because DNA is a negatively charged molecule, due to its phosphate groups, and so will travel towards the anode of the electric currect, the smaller and faster pieces going further.

We all put our developed samples into the gel, and after about 20 minutes of sitting in the electric current, we were able to compare the results. The known sample from the approved forest showed three distinct bands of DNA, while the 2 samples from the lumber companies showed 2 and 1 respectively, meaning with wood was illegally taken from forests that may well be endangered or declining. The wood would be confiscated, and the companies fined, and any usable lumber will be distributed freely in order to ensure that nobody profits from damaging the threatened woodland.

It was very interesting to see how DNA is extracted and compared, as well as learning about its practical application when dealing with the illegal import and export of endangered species across the world. I hope that I have another chance to sample DNA again in the future.

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