Thesis (M. Phil.)--University of Hong Kong, 2007. / Title proper from title frame. Also available in printed format.

Thesis (Ph. D.)--University of Hong Kong, 2007. / Title proper from title frame. Also available in printed format.

Thesis (M.A.)--Trinity Graduate School, 2006. / Abstract. Includes bibliographical references (leaves 119-122).

Thesis--Copenhagen University. / Summary in Danish. Bibliography: p. 125-129.

Thesis (Ph.D.) - University of Queensland, 2004. / Includes bibliography.

Thesis (Ph.D.) - University of St Andrews, January 2008.

Thesis--Copenhagen University. / Summary in Danish. Bibliography: p. 125-129.

Thesis (M.A.)--Trinity Graduate School, 2006. / Abstract. Includes bibliographical references (leaves 119-122).

Mutagen-sensitive (mus) mutations in Drosophila melanogaster render developing flies hypersensitive to the lethal effects of DNA-damaging agents. In general, mus mutations identify DNA repair-related genes. In this study, 5 new second chromosome mus mutations (mus205B¹, mus208B¹, mus209B¹, mus210B¹ and mus211B¹), selected on the basis of sensitivity to methyl methanesulfonate (MMS), were characterized using a variety of genetic tests. One test measured the MMS-sensitivity of double mutant mus strains compared to their component single mutants. Mutant interactions were examined in 8 double mus and in 2 triple mus strains containing combinations of mus201D¹, mus205B¹, mus208B¹, mus210B¹ and mus211B¹ (or mus211B²). These analyses have revealed predominantly synergistic and epistatic responses to MMS. Taken together with the findings of previous genetic and biochemical studies of Drosophila mus strains, these results suggest that 3 major repair pathways may operate in flies to correct damage caused by MMS. Mutagen cross-sensitivity data and the results of the interaction studies suggest that mus mutations might serve as rapid and sensitive bioassays of somatic genotoxicity caused by mutagens and carcinogens. To explore this possibility, a simple mutagen test system was devised employing triple mutant mus strains. One strain (mus208B¹ mus210B¹ mus211B²) was tested for sensitivity to 14 mutagens/carcinogens and 2 non-carcinogens. Eleven of the mutagens/carcinogens were readily detected as genotoxic. Both non-carcinogens were non-genotoxic. These preliminary results demonstrate the feasibility (and some limitations) of the proposed somatic genotoxicity assay and emphasize the need for further test validation using a larger chemical data base. The temperature-sensitive lethal mutation mus209B¹ was subjected to extensive genetic analyses and to temperature shift experiments during development. This locus was found to encode a product(s) that (1) is essential for viability at virtually all pre-imaginal developmental stages (the latter half of pupation appears to be an exception), (2) is necessary for wildtype levels of resistance to the genotoxic effects of MMS and ionizing radiation, and (3) is required for female fertility. Confirmation of the pleiotropic nature of this mutation was obtained by meiotic and cytogenetic mapping studies and by complementation tests with a series of allelic mutations. The mus209B¹ phenotypes are similar to ones conferred by mutations in Drosophila and yeast that disrupt various aspects of chromosome metabolism. In this context, some possible roles for mus209B¹ are discussed. / Science, Faculty of / Zoology, Department of / Graduate

LCAT deficiency is a rare autosomal recessive disease characterized by low levels of plasma HDL and an inability of the enzyme lecithin:cholesterol acyltransferase (LCAT) to esterify cholesterol. An understanding of the structure and function of the LCAT protein will add significantly to the understanding of reverse cholesterol transport. This understanding can be gained, in part, by studying different mutations within the LCAT gene and their resultant phenotypes. Recombinant DNA technology has been used to determine the nature of a mutation in an LCAT gene of a previously described homozygote with this disorder. Southern blot analysis determined there were no major rearrangements in the genomic DNA at the LCAT locus. An attempt was made to follow segregation of the mutant alleles in three generations of a large pedigree by linkage analysis. There are known polymorphisms at the haptoglobin (Hp) locus, which is linked to LCAT on the long arm of chromosome 16, and in the adenosine phosphoribotransferase (APRT) and choesterol ester transfer protein (CETP) loci which are also on the long arm of chromosome 16, but have not been shown linked to LCAT. The information gained was uninformative in this pedigree. An extensive restriction fragment length polymorphism (RFLP) search in the immediate vicinity of the LCAT gene did not reveal any polymorphic sites. 2.4 kb of the ⋋ phage clone SF1020, obtained from one of the homozygotes, containing exons 1-5 plus 0.5 kb of DNA 5¹ to the LCAT gene, but not exon 6, was subcloned into M13 and sequenced. A cytosine to thymidine (C->T) transition was discovered in exon 4. This would result in a substitution of tryptophan for arginine at amino acid 135. The amino acid arginine is positively charged and resides in one of the most highly charged segments along the amino acid chain of the LCAT protein indicating that this region is likely involved in protein folding. Tryptophan, on the other hand is the most hydrophobic of the amino acids and would, therefore, severely disrupt the interaction of charged amino acids in that region, preventing normal folding of the LCAT protein. / Medicine, Faculty of / Medical Genetics, Department of / Graduate