Tucker ’12 Analyzes DNA for Rattlesnake Population Research

April 24, 2012 Purnell Cropper

By Chris Macchi ’12

Last summer Biology major Sharese Tucker ’12 tested the DNA of timber rattlesnake populations (Crotalus horridus) found in Westmoreland County, Pa., with the hopes of making conclusions about the factors causing their genetic variation. Mentored by Dr. Lauretta Bushar, Tucker has continued last summer’s research into her final semester at Arcadia by taking the project on as her senior thesis.

In addition to advancing the body of knowledge collected on rattlesnake populations and albinism, this research has exposed Sharese Tucker to hands-on experiential learning that will go a long way in preparing her for the future. “I have learned a lot from doing research with Dr. Bushar…. It’s one thing to read about PCRs [Polymerase Chain Reactions, a technique used to multiply pieces of DNA for genomic analysis], but it’s another thing to actually do it.”

Dr. Bushar says that students aren’t the only ones who benefit from collaborative research. “I chose to become a faculty member at Arcadia because of the opportunity to work closely with undergraduate students both in the classroom and in the research laboratory. I enjoy working with students and watching their intellectual growth as they transition from newly minted high school graduates to college graduates.

“Research experience provides our students with skills that make them more marketable upon graduation. However, more importantly, research gives students an understanding that science is not about memorizing a bunch of facts but rather that science is a method of inquiry that allows us to learn about the world around us.”

The pair’s research seeks to determine the causes behind an albino population of timber rattlesnakes living in the southwestern Pennsylvania county. A fairly rare phenomenon, albinism is passed down from generation to generation, thus allowing it to continue to spread within a population. Since it can be traced through heredity, researchers can study populations with albino individuals to try to determine how or why it is present. However, a whole population made up of the unpigmented individuals raises questions about the forces acting upon the population as a whole.

Oftentimes, biologists are able to conclude that atypical populations arise due to reproductive isolation, a trend that represents a barrier between the atypical population and other, more normal populations, preventing mating from occurring between the two. Reproductive isolation of a population forces inbreeding and the recycling of genes, which ultimately would lead to a decrease in the genetic variation within that population. By analyzing the DNA of both the albino and normal populations, Tucker and Bushar are able to determine genetic variation within each and draw inferences about the cause of the differences.

In their research, Tucker and Bushar expected results to dictate that the population was albino because it was reproductively isolated and constantly interbreeding. Although the albino population was found to have lower genetic variation than other normal populations, this difference in variation was not significant enough to attribute it exclusively to isolation. These results, though not expected, are still valuable in the study of albino rattlesnake populations and environmental pressures.

Arcadia’s small class sizes and opportunities to do research alongside faculty aren’t the only things that have made a difference for Tucker. Student mentors in the Pre-Med Club helped her secure volunteer experience at Doylestown Hospital, provided tips for improving her résumé, and gave support in preparing for medical school applications. She has been volunteering at Doylestown Hospital since May 2010, and spent the summer of 2011 working as an intern. Tucker anticipates pursuing a career in pediatrics while awaiting acceptances from medical school programs for next year. In the meantime, she plans to continue her undergraduate research career by assisting Bushar on another project working with Boa constrictors on the island of Aruba this summer.

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