“Where are you from?” Everyone gets asked that question at some point in their lives, and it is often part of regular conversation on college campuses.Of course, you know where you were born, but that is not all there is to it. After all, people have been migrating from continent to continent for thousands of years. What if you could scientifically trace your ancestry back through thousands of years and find out the origin of part of your DNA? This is exactly what Assistant Professor of Biology Luana Maroja, who conducts research on human evolution and Professor of Biology Marsha Altschuler, a specialist in genetic regulation, are trying to do: They are unlocking the secrets of our geneology in unlocking the secrets of our DNA. They are sequencing the mitochondrial DNA of students and faculty at the College in an effort to find out where in the world they all come from.
Mitochondrial DNA, which is found in a cell’s mitochondria, the energy producing part of the cell, is separate from a person’s double-helixed DNA and is only inherited from the female line. Due to migration of populations throughout human history, different continents gave rise to different mutations in mitochondrial DNA, and these mutations can be ordered and kept as representative sequences of their continents. These mutations occur in a specific region of mitochondrial DNA, called the hypervariable region, due to its tendency to accumulate a variety of mutations. Since this region doesn’t code for proteins, mutations in the area are not harmful to the individual carrying them and so can be passed down through generations through the maternal line. This is how a mutation that occurred thousands of years ago can be found in an individual today.
To determine where students’ DNA comes from, Maroja and Altschuler sequence the students’ DNA and compare it to different haplotypes – previously recorded sequences that represent specific mutations. Therefore, a student with a specific set of mutations will have a particular haplotype, which can be shown to have originated in a specific continent a certain number of years ago. “It’s just the history of human populations, in terms of where they originated and started spreading. Small groups carrying a distinctive bit of mitochondrial DNA migrate, a change occurs, and it builds up in the population that expands,” Altschuler said.
Once Maroja and Altschuler have collected and sequenced the haplotypes, they will then be plotted on a mitochondrial tree in which each color represents a continent and each purple or red dot will represent a College student or faculty member and his or her own haplotype, respectively
This project was first created a couple of years ago by a different faculty member, but Maroja and Altschuler are continuing to contribute to it. Maroja has been working on the project since 2011 when she first took mitochondrial DNA samples from all of the biology professors and the next year from all of the psychology professors. Students in evolution classes will also get a chance to sequence their own DNA, and this month the professors asked a group of volunteers to get involved in the process as well. “This is actually a project that [Maroja] does in Biology 305,” Altschuler said. “The reason we’re doing it at this time is because in early February we have a performance at the ’62 Center for Theatre and Dance by Baba Brinkman, who is a rap artist, and he does a rap number that says “We’re all Africans,” so we wanted to get some student interest in that performance.” According to the mitochondrial tree, Brinkman is correct, genetically speaking – since humans originated from Africa, all haplotypes can be traced back to the continent.
There have been some interesting findings in this project, specifically with the College’s faculty. “We’ve found that Williams faculty is not very diverse. They tend to have the same mitochondrial DNA, which seems to come from Europe,” Altschuler said. For some professors, the research uncovered a case of mistaken heritage. “There were two or three cases where people believed that they were European, but when they get sequenced, they have South American mitochondrial DNA. It’s actually very common, and so far everyone that came from South America had the South American mitochondrial DNA and thought they would have the European mitochondrial DNA,” Maroja said. She explains that this probably occurred due to the fact that, back then, when a South American female married a European male, she lied and stated that she, too, was European. “The legend gets passed on to the offspring, and they don’t question it, and on and on, and a few generations later, someone discovers that the European thing was a myth. That’s very common,” Maroja said.
The mitochondrial tree showing the lineage of the College’s students and faculty will be posted during the first week of February and displayed in the lobby of the ’62 Center. Thanks to the professors’ project, we’ll be able to see the diversity in our campus not just in terms of where we were born, but also in our ancestry and in the DNA we carry. “You’re learning not about your personal history or family history but about a bit of DNA and its history,” said Altschuler. “You’re carrying DNA that has a legacy.”