Date of Award:
Doctor of Philosophy (PhD)
Animal, Dairy, and Veterinary Sciences
Department name when degree awarded
James T. Bowman
Two manifestations of gene regulation- - dosage compensation and ontogenic regulation--were examined in normally positioned and relocated v+ genotypes in Drosophila melanogaster to determine the role of gene position in these control functions. Enzyme assays, used as criteria of gene activity, were performed on various genotypes containing different doses of v+ in normal and relocated positions in male and female flies. The results indicate that although differently position e v+ genes may specify different tryptophan pyrrolase activities, they still show dosage compensation. In each case, the enzyme activity associated with each gene, either on the X, Y, or third chromosome, is twice as much in males as it is in females. This indicates that dosage compensation is not confined to the gene when located on the X chromosome.
In order to determine if the pattern of activity of the gene during ontogeny is altered by relocation, T(1;3)rasv genotypes and wild type controls were assayed at the same stages of development. The experimental design allowed a comparison of the ontogenic expression of three different genes—v+ , Zw, and Pgd--through the activities of their associated enzymes. The results indicate that changing the gene's position may alter its ontogenic expression. Animals with v+ on the third chromosome have a unique peak of tryptophan pyrrolase activity in larvae which is not present in wild type. The activity in this peak is at least 10 times higher than that observed in 72-hour wild type larvae, in fact, higher than that observed in any normal genotype at any time during development. With the exception of this peak, the developmental curves of enzyme activity are similar, although the relocated genes specify consistently lower enzyme activities than do normally positioned genes. The unique peak is not the result of a general physiological effect since the patterns of Zw and Pgd activity appear to be the same in wild type and translocated v+ genotypes. The relevance of the data to earlier studies and to models for gene regulation is discussed.
Tobler, Jack E., "The Effect of Chromosomal Position on Dosage Compensation And Ontogenic Expression of the V+ Gene in D. Melanogaster" (1971). All Graduate Theses and Dissertations. 7827.
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