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Snell, Terry W.

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Now showing 1 - 8 of 8
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    A biochemical, genetic, and genomic investigation of the evolution and ecology of sexual reproduction
    (Georgia Institute of Technology, 2010-11-17) Snell, Terry W. ; Kubanek, Julia ; Georgia Institute of Technology. Office of Sponsored Programs ; Georgia Institute of Technology. School of Biology ; Georgia Institute of Technology. Office of Sponsored Programs
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    Stress gene expression patterns in hematypic corals exposed to dredged ...
    (Georgia Institute of Technology, 2009-06-22) Snell, Terry W. ; Georgia Institute of Technology. School of Biology ; Georgia Institute of Technology. Office of Sponsored Programs ; Georgia Institute of Technology. Office of Sponsored Programs
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    Assessing the Genotoxic Effects of Microparticulate Exposure in Drosophila Melanogaster
    (Georgia Institute of Technology, 2011) Kabir, Fahim ; Snell, Terry W. ; Danielson, Chris
    Exposure to microparticulate matter and endocrine disruptors has been linked to severe pathological and disruptive effects on human health. Airborne microparticles are confirmed vectors for various pulmonary and cardiovascular conditions as well as adverse genotoxic and cytotoxic effects. Endocrine disruptors are especially detrimental since they selectively interfere with the sex hormone functions of the host organism and can potentially disrupt ecosystems by hindering reproduction in affected species. Despite the fact that there are numerous studies assessing the cytotoxic effects of airborne microparticulate matter, there is a clear deficiency of conclusive data and topical research assessing the genotoxic effects of microparticles on organisms. The aim of this study was to evaluate the significance of microparticulate exposure in an urbanized setting in order to assess whether anthropogenic causes are producing detrimentally quantifiable genotoxic effects and possibly endocrine disruption. Drosophila melanogaster was used as a model test subject to analyze for survivorship, induced genotoxicity, and distorted sex ratios across generations. Samples of microparticulate matter were collected from four locations of varying degrees of urbanization and incorporated into the parental generation and observed over two generations. Microparticulate exposure did in fact have an observable generational selection effect on D. melanogaster. We also observed distorted sex ratios in the F1 generation; however, endocrine disruption was not attributable to exposure. Based on a comet assay, we found clear indications that genotoxic damage was linked to the extent of microparticulate exposure.
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    Genetic determinants of mate recognition in Brachionus manjavacas (Rotifera)
    (Georgia Institute of Technology, 2009-09-09) Snell, Terry W. ; Shearer, Tonya L ; Smith, Hilary A. ; Kubanek, Julia ; Gribble, Kristin E. ; Welch , David B. Mark ; Georgia Institute of Technology. School of Biology ; Woods Hole Oceanographic Institution. Marine Biological Laboratory
    Background: Mate choice is of central importance to most animals, influencing population structure, speciation, and ultimately the survival of a species. Mating behavior of male brachionid rotifers is triggered by the product of a chemosensory gene, a glycoprotein on the body surface of females called the mate recognition pheromone. The mate recognition pheromone has been biochemically characterized, but little was known about the gene(s). We describe the isolation and characterization of the mate recognition pheromone gene through protein purification, N-terminal amino acid sequence determination, identification of the mate recognition pheromone gene from a cDNA library, sequencing, and RNAi knockdown to confirm the functional role of the mate recognition pheromone gene in rotifer mating. Results: A 29 kD protein capable of eliciting rotifer male circling was isolated by high-performance liquid chromatography. Two transcript types containing the N-terminal sequence were identified in a cDNA library; further characterization by screening a genomic library and by polymerase chain reaction revealed two genes belonging to each type. Each gene begins with a signal peptide region followed by nearly perfect repeats of an 87 to 92 codon motif with no codons between repeats and the final motif prematurely terminated by the stop codon. The two Type A genes contain four and seven repeats and the two Type B genes contain three and five repeats, respectively. Only the Type B gene with three repeats encodes a peptide with a molecular weight of 29 kD. Each repeat of the Type B gene products contains three asparagines as potential sites for N-glycosylation; there are no asparagines in the Type A genes. RNAi with Type A double-stranded RNA did not result in less circling than in the phosphate-buffered saline control, but transfection with Type B double-stranded RNA significantly reduced male circling by 17%. The very low divergence between repeat units, even at synonymous positions, suggests that the repeats are kept nearly identical through a process of concerted evolution. Information-rich molecules like surface glycoproteins are well adapted for chemical communication and aquatic animals may have evolved signaling systems based on these compounds, whereas insects use cuticular hydrocarbons. Conclusion: Owing to its critical role in mating, the mate recognition pheromone gene will be a useful molecular marker for exploring the mechanisms and rates of selection and the evolution of reproductive isolation and speciation using rotifers as a model system. The phylogenetic variation in the mate recognition pheromone gene can now be studied in conjunction with the large amount of ecological and population genetic data being gathered for the Brachionus plicatilis species complex to understand better the evolutionary drivers of cryptic speciation.
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    Development of biomarkers for coral reef bioassays
    (Georgia Institute of Technology, 1998) Snell, Terry W. ; Georgia Institute of Technology. School of Biology ; Georgia Institute of Technology. Office of Sponsored Programs ; Georgia Institute of Technology. Office of Sponsored Programs
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    Stress gene expression patterns in hematypic corals exposed to dredged.....
    (Georgia Institute of Technology, 2007-02-23) Snell, Terry W. ; Georgia Institute of Technology. Office of Sponsored Programs ; Georgia Institute of Technology. School of Biology ; Georgia Institute of Technology. Office of Sponsored Programs
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    Chemical communication among Marine Zooplankton
    (Georgia Institute of Technology, 1993-08) Snell, Terry W. ; Georgia Institute of Technology. Office of Sponsored Programs ; Georgia Institute of Technology. School of Biology
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    Development of coral surrogates for coral reef bioassays
    (Georgia Institute of Technology, 1996-02) Snell, Terry W. ; Georgia Institute of Technology. Office of Sponsored Programs ; Georgia Institute of Technology. School of Biology