Research of the clones: How a campus lab works to understand the Domain

By Samuel Carter
Contributing Writer

I entered Spencer 157 with Cade Sterling (C’22), the lab coordinator, to interview him about his team’s current research. We found Andrew Hanissian (C’20) leaned over the counter, extracting DNA. For Sterling, Hanissian, and the four other students who will work in the lab this week, nice weather doesn’t mean an afternoon exploring the Domain. Instead, they work to understand how Sassifras albidum, a tree native to the region commonly known as the Sassafras tree , reproduces. 

Professors Jason Palagi and Jonathan Evans supervise the lab. Sterling and Hanissian both began their work last summer under Palagi. At the end of the summer, the lab partnered with the Sewanee Herbarium, headed by Evans, to continue the research.

“The Sassafras tree is known to reproduce clonally, but previous studies have been inconclusive,” said Sterling, who hopes the research will answer correctly the question of ‘how?’ that previous researchers have not.

The process of answering this question can be lengthy and tedious. First, the lab has to collect sassafras leaves from across the Domain from 500 individual trees. The DNA of each of these samples must then be extracted and tested. 

DNA extraction is no quick task. The team begins with homogenization–smashing the leaves to a fine pulp. They then heat the leaves to finish breaking open the cells. This makes the DNA accessible but indistinguishable from other molecules, like proteins. To get the DNA—and only the DNA—the team must perform several steps that wash away unwanted molecules and pull out the wanted DNA. Finally, DNA has been extracted. The result is a network of delicate, limp fibers.

The team then amplifies the extracted DNA by running polymerase chain reactions, or PCR. Sterling pats the PCR machine with a certain amount of pride and familiarity. He, like any good researcher, has spent his fair share of time running the machine. Without it, the research would be practically inefficient. PCR results in millions of more copies of DNA from that which was originally extracted. More DNA means more time testing and less time collecting samples.

After running the PCR and amplifying the DNA, the project grows much larger than just Spencer 157 or even Sewanee: the samples are sent to Yale for genotyping. At Yale, technicians run fragment analysis of the DNA. Fragment analysis involves labeling and separating the DNA samples, then compares them. This size comparison reveals the size of short, repeating DNA patterns called microsatellites. These results will be sent back to the team at Sewanee.

The results reveal which individual sassafras trees are clones. If two tree samples have the same microsatellite size, then the team has found clones. Using this information, the team can understand the frequency of cloning among the trees and at what range one tree can produce clones.  

The purpose of this research and its many tests holds an important clue to better understanding clonal reproduction across temperate tree species, not just sassafras on campus. Since the field has few accurate or thorough descriptions of clonal reproduction, the results may explain parts of clonal reproduction never before understood. 

While Sterling, Hanissian, and their partners understand the significance of their work, it doesn’t seem to be the reason they spend their afternoons in the lab. Instead, a love for science and a passion to understand it better drives them. They hope that this love will be passed onto others.

Hanissian encourages any student interested in science to connect with professors and seek out research opportunities. “It’s not difficult to get into research if you take the right steps, and it’s incredibly worthwhile,” he said. He also praised Sewanee for “taking care” of its students and offering opportunities for lab research and faculty mentorship.

Sterling, who entered Sewanee with an interest in scientific research, said, “my time in the lab has only convinced me that it’s my interest even more.” He wants to make a career of research but also wants to spend time teaching others about science and instilling the same passion. Sterling, who has been mentored by Professors Palagi and Evans, said that he “looks forward to mentoring students.” Later this semester, he and the rest of the team will soon have the opportunity to begin educating others about science, as they travel to schools in the area to share their love for research.

All Sewanee students benefit from this research team, as well. With each strand of DNA they extract, PCR they run, and piece of data they collect, we better understand the world that surrounds us. We better appreciate the trees that tower above us as we peer off Morgan’s Steep. We better love and take care of this beautiful Mountain.