Genetics - Theses
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ItemA genetic investigation of congenital defects in alpacas( 2013)The aim of this PhD project was to understand the genetic mechanisms contributing to congenital defects in alpacas. Alpaca veterinarians report a prevalence of congenital defects much higher than any other livestock species. A reduction in genetic diversity due to mating between closely related individuals can cause congenital defects. In this study, inbreeding coefficients estimated from genomic data were compared between individuals with congenital defects and healthy individuals. Australian alpacas with congenital defects did not show significantly higher levels of inbreeding than alpacas without diagnosed defects. Therefore, high levels of inbreeding cannot explain the prevalence of congenital defects in Australian alpacas. One common congenital defect is the blue-eyed white phenotype which is characterized by solid white fleece, two blue eyes and often deafness. A genetic investigation of the blue-eyed white phenotype and the mapping of this trait form the second aim of this project. Case-control association analyses were performed and KIT was identified as the gene likely to be responsible for this trait. Two haplotypes were present in BEW (blue-eyed white) individuals and this suggested that two mutations contribute to this phenotype. Next-generation sequencing was used to identify possible causative mutations. Single nucleotide polymorphism analysis was used to refine the region which contains the mutations responsible for this trait and to examine the linkage disequilibrium in this region. The experimental results from this thesis were used to formulate a model for the genetic inheritance of the BEW phenotype in alpacas. The genetic markers examined in the study have the potential to provide a useful genetic test for breeders who view the BEW phenotype as a congenital defect which should be culled from the population. Together the aspects of this project aim to provide breeders with information on the genetic diversity of Australian alpaca stock as well as provide a genetic tool to enable the elimination of a deleterious phenotypic trait.
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ItemThe genetics of resistance to lufenuron in Drosophila melanogaster( 2005-02)The rise of large scale agriculture in the 20th century created the need for effective strategies to control insect pests. Treatment with chemical insecticides has been a weapon of choice, but the inevitable evolution of resistance has followed in many insect species. Resistance represents a major challenge, not only for agricultural production, but also for environmental preservation and human health. Two major options for resistance have been identified, and these are target-site based and metabolic-based resistance. Much insecticide resistance research focuses on identifying these mechanisms through genetic and molecular analysis. The insecticide lufenuron is the focus of this study. It belongs to a novel insecticidal group called the insect growth regulators, which were introduced in 1970s as highly selective insecticides with low vertebrate toxicity. Resistance to lufenuron in the non-pest species Drosophila melanogaster has been observed in field populations, despite the lack of field usage of lufenuron (Wilson & Cain, 1997; O’Keefe, 1997). This study has taken advantage of this phenomenon to investigate resistance mechanisms in natural populations. At least two detoxification mechanisms were identified. (For complete abstract open document)