Month: June 2016

Gel Electrophoresis

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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.

Wakehurst Meadow Survey

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The Wakehurst Place Botanical Gardens are one of the last places in Britain where it is possible to find natural meadow or forest. Most meadows across the country are scoured of their native inhabiting grasses and flowers through centuries of management, farmers choosing to plant crops or new, often Italian, grasses that take more easily to fertilisers and provide a healthy and easy to grow feedstock for their animals. This makes true natural meadow, with actual British wildlife very rare, so it was interesting to see what species lived in one of the last preserved meadows.

Using measuring tape and a set of quadrats, we created a transect leading from the middle of the meadow towards the managed treeline of the neighbouring forest. A quadrat is a square metal frame, 1m by 1m in area, used by Biologists to take a sample of a habitat and measure the diversity and species abundance of the whole area. It would be ridiculous and time consuming to search the whole field and note down what lived there, but by taking this sample, I could get an idea of what lived in the rest of the field, while also seeing how the species abundance changed as I approached the forest.

In the centre of the field the field grass coverage was near absolute, with gaps in the green breaking out where moles had previously tunnelled to the surface, and apart from the occasional buttercup or ribwort plantain, not many larger plants lived there. As we approached the forest line, however, we found a greater abundance of different plants, the biodiversity increasing as the shade of the forest made it harder for the grass to dominate the land. Species like knapweed, devil’s-bit scabious, a flower that acts as home to larvae of Marsh Fritillary butterflies, and Birdsfoot Trefoils, sometimes referred to as ‘Bacon and Eggs’ due to the red and yellow colouration of their flowers. Interestingly, the Trefoil releases dangerous cyanide when it is chewed, although it is in such small amounts it is unlikely to be harmful to larger mammals such as humans.

The Birdsfoot Trefoil sitting within my quadrat.

At the edge of the oak woodland, the ground gave way to ferns, before dying out to woodland plants, such as violets and archangels, covered in tiny white spots, that act as magnifying  glasses to focus light onto their leaves. Just before the meadow became forest, we found a group of three tiny Common Frogs, freshly transformed from tadpoles and making their way from the lake at the base of the meadow deeper inland. It was great to see the variety of interesting plant species that grow in our native meadows, especially as it is so easy to forget how amazing our own country is, when shown the brightly coloured rainforests of Brazil, or the volcanic tundra of Greenland. Even such a short way from home I am able to stand in an incredibly rare environment.