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Samantha C. Lewis |
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Undergraduate Research Assistant
Research Interests: I am sequencing the mitochondrial genomes of two free-living nematodes: strains AF36 (sexual) and PS1579 (obligate parthenogen) of the genus Panagrolaimus to evaluate the degree to which reduced selection efficiency allows the accumulation of deleterious mutations. Sequence changes between ancestrally asexual PS1579 and its closest sexual ancestor, AF36 may provide valuable insights into the effects of reproductive mode on mitochondrial genome evolution. Since I began this project in September 2006, I have sequenced approximately 60% of the PS1579 and 40% of the AF36 mitochondrial genomes using a PCR/primer walking approach. My sequencing efforts have revealed some exciting preliminary data. In addition to several insertions, deletions and possible pseudogenes, PS1579 and AF36 are divergent with respect to at least one tRNA. The arginine tRNA typically located between Cytochrome b, the mitochondrially encoded subunit of the ubiquinol-cytochrome c reductase complex, and NADH dehydrogenase subunit 2, the external dehydrogenase that provides cytosolic NADH to the respiratory chain, is absent in PS1579. tRNA translocations have been documented in other metazoan lineages; however, no metazoan has ever been documented as completely missing an essential mitochondrial tRNA. Such an extreme mutation would drastically affect fitness and could be the result of reduced selection efficiency associated with asexuality.Links:
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