Mentzelia and DNA

During the last year, I’ve been doing research with Dr. Brokaw on the genetics of species in the genus Mentzelia. This research involves sequencing the DNA of these plants and looking for similarities and differences between multiple species in this genus in order to see if the regions we’re using are a definitive indicator of a difference between the species. In addition, we’re using it to compare a few species in particular, with a special focus on Mentzelia monoensis. This species, thus far, has only been found in one region in Mono county, California. Because the traditional means of differentiating it from other species, it’s seeds, is not always feasible depending on the season and the presence of seeds in a particular sample, it’s important to be able to identify it through alternative means. To this end, we are comparing the chloroplast DNA in Mentzelia monoensis to species that are difficult to differentiate by sight alone.

My time in the lab has primarily been dedicated to the extraction of the DNA and interpreting the results of this DNA. The first step in the process is the collecting of a sample from a pressed plant, and grinding the plant matter so that the plant cell proteins don’t interfere with the DNA extraction process. This is probably the most tedious step in the process, especially when working with many samples at once. Often the pressed samples are difficult to get any leaves from, and moving the leaves takes some precision. The grinding itself can be pretty tiring on the fingers, as the leaf samples are rather small and therefore necessitate using a very small pestle to grind them, which can strain one’s fingers after a while. Even though this step can be boring, it’s also very interesting. The samples we use often are from very different geographic regions, given to us by herbariums across the area that we’re studying. In addition, the samples are very frequently older than myself; of the oldest samples we discovered was over 100 years old!

The rest of the process often goes much smoother, with enough to do to remain interesting. After extracting the DNA by grinding it, we have to purify the DNA and then amplify it through a polymerase chain reaction that essentially copies the DNA several times. We then send the DNA off to a lab for them to sequence, and we receive the results, correct any errors, and compare them to previous samples. The entire process has been fairly exciting. It’s been great to see our results accumulating over the last six months and supporting our hypotheses about the plants we’re studying. I’ve learned quite a bit about the research process, especially how to avoid mistakes (it can be rather difficult to figure out what a sample is when you rub half the label off!), and I’ve gotten a lot of valuable lab experience working with machines and processes that I might encounter later in my life. While we haven’t been able to get many results recently because we haven’t quite mastered our new extraction process, I’m looking forward to continuing to proceed and eventually get more done. Our results have thus far been interesting, and I’m excited to see where they go in the future.

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