Matching Items (2)
Filtering by
- All Subjects: Biology
Description
Mutation is the source of heritable variation of genotype and phenotype, on which selection may act. Mutation rates describe a fundamental parameter of living things, which influence the rate at which evolution may occur, from viral pathogens to human crops and even to aging cells and the emergence of cancer. An understanding of the variables which impact mutation rates and their estimation is necessary to place mutation rate estimates in their proper contexts. To better understand mutation rate estimates, this research investigates the impact of temperature upon transcription rate error estimates; the impact of growing cells in liquid culture vs. on agar plates; the impact of many in vitro variables upon the estimation of deoxyribonucleic acid (DNA) mutation rates from a single sample; and the mutational hazard induced by expressing clustered regularly interspaced short palindromic repeat (CRISPR) proteins in yeast. This research finds that many of the variables tested did not significantly alter the estimation of mutation rates, strengthening the claims of previous mutation rate estimates across the tree of life by diverse experimental approaches. However, it is clear that sonication is a mutagen of DNA, part of an effort which has reduced the sequencing error rate of circle-seq by over 1,000-fold. This research also demonstrates that growth in liquid culture modestly skews the mutation spectrum of MMR- Escherichia coli, though it does not significantly impact the overall mutation rate. Finally, this research demonstrates a modest mutational hazard of expressing Cas9 and similar CRISPR proteins in yeast cells at an un-targeted genomic locus, though it is possible the indel rate has been increased by an order of magnitude.
ContributorsBaehr, Stephan (Author) / Lynch, Michael (Thesis advisor) / Geiler-Samerotte, Kerry (Committee member) / Mangone, Marco (Committee member) / Wilson, Melissa (Committee member) / Arizona State University (Publisher)
Created2023
Description
Phenotypic evolution is of great significance within biology, as it is the culmination of the influence of key evolutionary factors on the expression of genotypes. Deeper studies of the fundamental components, such as fitness effects of mutations and genetic variance within a population, allow one to predict the evolutionary trajectory of phenotypic evolution. In this regard, how much the change in mutational variance and the ongoing natural selection influence the rate of phenotypic evolution has yet to be fully understood. Therefore, this study measured mutational variances and the increasing rate of genetic variance during the experimental evolution of Escherichia coli populations, focusing on two growth-related traits, the populational maximum growth rate and carrying capacity. Mutational variances were measured by mutation-accumulation experiments, which allowed for the analysis of the effects of spontaneous mutations on growth-related traits in the absence of selection. This analysis revealed that some evolved populations developed a higher mutational variance for growth-related traits. Further investigation showed that most evolved populations have also developed a greater mutational effect, which could explain the increase in mutational variance. Finally, the genetic variances for most evolved populations are lower than expected in the absence of selection, and the involvement of either stabilizing or directional selection is evident. Future experiments with a larger sample size of experimentally evolved populations, as well as more intermediate timepoints during experimental evolution, may provide further insight regarding the complexities of the evolutionary outcomes of these traits.
ContributorsGonzales, Jadon (Author) / Lynch, Michael (Thesis advisor) / Geiler-Samerotte, Kerry (Committee member) / Ho, Wei-Chin (Committee member) / Arizona State University (Publisher)
Created2023