UBC Theses and Dissertations
Dispersal of transposable elements Meister, Gerald Alan
This thesis describes four related sets of experiments: The first three experimental series investigated the dynamics of transposable element (TE) spread and accumulation following the introduction of low frequencies of Drosophila melanogaster containing specific TEs into populations that previously lacked the elements. In the first series (Chapter II), flies containing P elements with an inserted alcohol dehydrogenase gene were introduced. DNA hybridization assays showed that, despite an approximate three-fold increase in size over unmodified elements, the P element constructs were capable of rapid dispersal through the experimental populations. Moreover, assays for alcohol dehydrogenase activity revealed that many of the dispersed genes still encoded an active product. In the second series of experiments (Chapter III), hobo element containing flies were introduced. DNA hybridization assays showed that hobo elements were present within virtually all individuals within eight generations. The mean amount of hobo hybridizing DNA per element containing individual decreased in the first few generations, but then increased and stabilized at approximately 50% of that present within the element donating strain. The total hobo hybridizing DNA in the populations steadily increased until it also stabilized at about 50% of the amount in the donor strain. In the third series of experimental populations (Chapter IV), genomes containing both P and hobo elements were introduced. Within 8-10 generations both elements spread to all genomes within these populations and the P element DNA rapidly accumulated to the amount present in the elementdonating strain. However, as with the populations in which only hobo elements were introduced, the hobo DNA accumulated to much less than that present in the donating strain. In the final set of experiments (Chapter V), a differential DNA hybridization method for detecting moderately repetitive strain-specific TEs was developed. To demonstrate the effectiveness of this procedure, a lambda genomic library was prepared from DNA of a D. melanogaster strain that contained both P and hobo TEs. Duplicate plaque lifts of this library were then hybridized to DNA from this strain and to DNA from a strain which lacked the TEs. Differentially hybridizing plaques were isolated. Finally, reprobing with TE sequences demonstrated that plaques that hybridized differentially to the genomic probes did indeed contain TEs. This differential screen was then applied to several pest insect species in preliminary experiments.
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