Physical Sciences

Parsons, Travis; Lippert, Peter; Bartley, John (University of Utah)
Faculty Advisor: Lippert, Peter (University of Utah - College of Mines and Earth Science, Geology & Geophysics); Bartley, John (University of Utah - College of Mines and Earth Science, Geology & Geophysics)

Field observations and geochronological measurements of plutons in Yosemite Valley suggest that plutons grow incrementally as a series of stacked sheets of smaller intrusions (i.e., dikes and sills) (Coleman et al., 2004; Glazner et al., 2004; Bartley et al., 2006). This interpretation is in contrast to the traditional view of pluton emplacement through crystallization of a single, massive magma chamber. Most of the observations supporting incremental pluton emplacement use the relationship between zircon U-Pb dating of pluton sections and estimated granitic magma cooling rates to argue that a single magmatic event would crystallize significantly faster than the geochronologic data permit. Incremental pluton emplacement also predicts specific relationships between the age of intruded sheets of magma and the original orientation of these sheets, such that older sheets are expected to be tilted or deformed more than younger sheets. Here we test this prediction of differential tilting by measuring the paleomagnetic inclination preserved in well-dated and structurally characterized sheets of the Tuolumne Intrusive Suite. Magnetic inclination provides a tilt-meter with respect to the Earth's magnetic field direction at the time of pluton emplacement; the reference inclination assuming an untitled pluton is known from independent data sets. We also present rock magnetic data (temperature-dependent magnetic susceptibility, magnetic remanence characteristics) and results from petrographic investigations to characterize the mineralogy and stability of the magnetization. Our results suggest that the low-titanium magnetite remanence carriers are primary and are not biased by secondary magnetizations. The distribution of magnetic inclinations in our sample set — in which older sheets on the periphery of the pluton are shallower than those in younger, more interior sheets, and with respect to the reference inclination — is consistent with predictions from the incremental pluton emplacement hypothesis.

White, Michelle; Koury, Spencer; Phadnis, Nitin (University of Utah)
Faculty Advisor: Phadnis, Nitin (University of Utah, School of Biological Sciences)

Sex-ratio chromosomes in Drosophila pseudoobscura are of particular interest because they violate not one, but all three of Mendel's laws of genetics. These special X chromosomes distort the ratio of X and Y-bearing sperm, which leads to biased sex-ratios within the offspring. Although such transmission ratio distortions have been observed from as early as 1928, very little is known about the systems of genes responsible for sex-ratio chromosomal drive due to several complications with traditional methods. Here, we perform one part of a three-part experimental series that attempt to dissect and identify not only the genes involved but also its mechanism. Specifically, this approach will use saturation chemical mutagenesis to knock out every gene on sex-ratio (SR) chromosomes. In order to accomplish this task as efficiently and timely as possible, several preliminary experiments were conducted. We provide the natural variability in SR chromosomal drive and the best statistical framework to analyze the actual mutagenesis experiment. Our results further provide an EMS dosage response curve for the D. pseudoobscura species which has only previously existed for D. melanogaster. These findings propose a reconsideration of the traditional methods used for studying SR chromosomal drive and suggest the mechanism behind the genes or systems of genes involved in this process.
With its rich biological history, the field of genetics has truly grown and expanded into all that we know today. With special regard to our very own Nobel Laureate, Dr. Mario Capecchi, The University of Utah has a dynamic relationship with the field of genetics. The Phadnis Lab plays an active role in this remarkable community and has answered several ideas in evolutionary conflict and speciation. Thus, as a student from the University of Utah studying genetics, it would be greatly interesting to be able to present my work at UCUR.