| الملخص: | <p>Glycosylation is a fundamental post-translational modification of proteins that occurs in all eukaryotes, but the biological significance of specific glycosylation structures is still largely unknown. We have chosen to study this process by cloning and characterizing the genes involved in the <em>N</em>-linked glycosylation pathway in <em>Drosophila melanogaster</em> and analysing mutants of these genes. Since this biochemical pathway for the production of <em>N</em>-linked glycans is considerably conserved, studying it in <em>Drosophila</em>, a useful organism for genetic research, should yield results applicable to other eukaryotes.</p> <p>This thesis describes the attempt to identify a <em>Drosophila</em> homologue of rat ER mannosidase and how this investigation resulted in the identification of a <em>Drosophila</em> cDNA with considerable homology to calnexin, an enzyme involved in the folding of <em>N</em>-glycosylated proteins. It also describes the cloning and characterization of the genomic sequence for the putative Golgi mannosidase II (<em>GmII</em>)* in <em>Drosophila</em>. The expression and control of expression of <em>GmII</em> have been investigated further, and have suggested expression of this gene throughout <em>Drosophila</em> development. Analysis of the <em>GmII</em> promoter region has shown expression from a TATA-less promoter contained within 288bp of sequence 5' to the start of transcription.</p>
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