Date of Award


Document Type


Degree Name

Bachelor of Science


Biological Sciences

First Advisor

Lynne Cassimeris

Second Advisor

Sean Buskirk

Third Advisor

Kaitlin Fisher


The yeast Saccharomyces cerevisiae is host to a selfish intercellular “Killer” virus. The yeast Killer virus is a double stranded RNA (dsRNA) that encodes a Killer toxin and confers immunity to the toxin. This virus was first described over 40 years ago, however, we still have a limited understanding of many aspects of the viral system, including frequency of viral recombination. Here we perform pairwise crosses between yeast strains containing known killer virus mutants that are unable to produce functional toxin. Successful mating events are then screened for killing ability to identify instances of recombination, which is denoted by reconstitution of killing phenotype. We have been unable to identify any instances of recombination in over 16 unique crosses where functional recombinants could have been generated. Sequencing reveals that both Killer virus variants are stably maintained as a heteroplasmic viral population. Our results suggest that killer virus has a low recombination frequency, which may extend to other encapsulated cytoplasmic RNA viruses as well.

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