Comparisons of Phylogenetic Tree Branch Lengths and Topologies of Influenza Virus Protein Sequences

Student Classification


Faculty Mentor

Dr. Scott H. Harrison



Document Type


Publication Date

Spring 2019


Influenza is a virus that has been known to infect thousands of individuals due to its ability to adapt to vaccines and other environmental changes. This virulence is partly due to the surface proteins hemagglutinin (HA) and neuraminidase (NA) that allow the virus to bind to its host and replicate. Studies have focused on these proteins, because their mutations directly influence the performance of the flu virus in host infection, but other proteins are also important in the growth and replication of the flu virus. Intracellular proteins, such as PB1 and PB2 are important for mRNA transcription processes in the virus. We compare HA to PB1 and PB2, to test whether branch lengths are longer for the HA gene, which is expected to have a greater degree of diversifying selection. For additional study, we compare different types of influenza: A, B, C, and D. Types A and B are more virulent to the population, while C and D are less virulent. We compare Type A and Type C to test the correspondence between how virulence relates to asymmetry of tree topologies. We have found that branch lengths vary as expected, and that Type A exhibits greater asymmetry compared to Type C.

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