Date of Award

2012

Document Type

Thesis

Degree Name

Master of Science (MS) in Biology

Department

Biology

First Advisor

Joanna Joyner-Matos

Second Advisor

A. Ross Black

Third Advisor

Molly K. Johnson

Abstract

"Since DNA mutations occur all the time and may have deleterious effects on fitness (survival and reproduction), organisms expend substantial metabolic resources to find and repair mutations. This metabolic expenditure is termed the cost of fidelity. If an organism is in "poor" condition and does not have enough metabolic resources, it may no longer be able to find and repair mutations (Agrawal 2002). In this thesis, we looked at whether physiological condition, measured as survival and development in the presence of an exogenous stress ('robustness'), correlated with mutation rate (experiments 1 and 2) or fitness (experiment 2). We measured physiological robustness of nematodes exposed to three different stressors: high heat, high free radicals, and high salt. The nematodes belonged to two Rhabditid nematode species and either had unmutated genomes (ancestral control) or genomes that had accumulated. In both high heat assays, we found that heat was effective at reducing nematode survival. We found that thermotolerance was higher in the HK104 strain of Caenorhabditis briggsae than the N2 strain C. elegans. Within the N2 strain, thermotolerance correlated with fitness. In experiments 1 and 2, exposure to high free radicals and high salt reduced nematode survival and slowed nematode development. The N2 strain was significantly more tolerant of free radicals and salt than the HK104 strain. Within the N2 strain, tolerance to free radicals and salt correlated with fitness. No robustness trait significantly correlated with mutation rates in experiment 1; we could not test for correlations with future mutation rates in experiment 2 because mutation rate data are not available at this time. Overall, robustness did not predict base substitution rate but was successful at predicting fitness when fitnesses were very different"--Document.

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