Thesis (Ph. D.)--University of Texas at Austin, 2004. / Supervisors: David M. Hillis and James J. Bull. Vita. Includes bibliographical references.

The serotype transformation system of the ciliate Paramecium primaurelia has been examined in order to elucidate the mechanism which controls its switch in gene expression. During temperature induced transformation of stock 168, the cell switches from the synthesis of the G surface antigen protein to that of the D surface antigen protein. In Chapter I the growth conditions and serotype expression of stock 168 of P. primaurelia have been examined. In Chapter II the organisation of the macronuclear genome has been investigated. The genome of Paramedium is simple, having little repetitive DNA and a complexity only 19 times higher than that of E. coli. The transcription of the macronuclear genome has been examined in Chapter III. Paramecium, like higher eucaryotes, contains polyadenylated RNA which has a heterogeneous size range. This polyA+ RNA is present in the cell at a broad range of intracellular frequencies, the least frequent class of polyA+ RNA being present at approximately 1000 copies per cell, while the higher frequency classes are present at 105 -106 copies per cell. The least frequent class of RMA is transcribed from up to 12% of the genome in cells grown at 25 ̊C and expressing the G-serotype, while cells grown at 32 ̊C appear to transcribe up to 22% of the genome, PolyA+ RNA has been translated by a wheat-germ in vitro translation system, in which polypeptides of up to 45Kdaltons were translated. There appears to be no synthesis of MA which is larger than polyA+ RNA, in contrast to the situation in higher organisms, although an examination of transcription units showed long nascent RNP. RNA and protein synthesis has been examined during the process of transformation, there appeared to be little change in either the pattern of RNA synthesis or the spectrum of proteins present. Polysomes containing antigen mRNA were specifically precipitated with antiserum. Although there was some non-specific precipitation, there was an enrichment of RNA in the size range 10 - 12S, the size expected of RNA coding for one antigen subunit.

The paper reviews the literature on polyploidy in respect to its possible application in forest tree breeding. The occurrence of spontaneous polyploidy in various species is enumerated and its qualities outlined. An account is presented of the success and failure thus far attained in the search for improved varieties of forest tree species through polyploidy. Finally, the potentialities of polyploidy in forestry are summarized and some recommendations concerning future lines of research are outlined. The experimental work in connection with this thesis was the preliminary investigation of Douglas fir (Pseudotsuga menziesii (Mirob) Franco) aberrants found each year among the seedlings at the B.C. Forest Service nursery in Duncan. These abberrants have been thought to be spontaneous autopolyploids because they resemble such polyploids found among nursery stock of other coniferous species elsewhere. This study, however, indicated beyond any doubt that these abberrants are not polyploids. Other possibilities which might have caused the aberrant form are discussed. / Forestry, Faculty of / Graduate

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Thesis (Ph. D.)--University of Missouri-Columbia, 2004. / Typescript. Vita. Includes bibliographical references (leaves 103-129). Also available on the Internet.

Thesis (Ph. D.)--University of Missouri-Columbia, 2004. / Typescript. Vita. Includes bibliographical references (leaves 103-129). Also available on the Internet.

Polyploidy is the presence of more than two sets of chromosomes. Polyploidy can be fatal, but when tolerated it always results in increased cell size. Polyploid vertebrates are not larger than their diploid counterparts, despite having larger cells, due to cellular rearrangements. An anuran example was investigated to determine potential effects of polyploidy on the process of hearing. The North American gray treefrogs, Hyla chrysoscelis and Hyla versicolor, are nearly identical with the exception that the latter is tetraploid. Morphology, hearing performance, and histology of the ears were assessed to identify differences in the tuning and sensitivity of hearing between these two species. Performance was measured as vibration of eardrums, distortions by hair cells in the inner ears, and electrical activity in an auditory nucleus of the brain. All morphological features were slightly larger in H versicolor than H chrysoscelis; including SVL, body mass, interaural distance, and eardrum diameter. Hearing sensitivity did not differ between the two species, while tuning differed at specific regions in the hearing pathway. Laser vibrometry revealed that spectral sensitivities at the eardrum and body wall were similar between the two species. Distortion-product otoacoustic emissions revealed a significant difference in tuning of the distortions produced by the hair cells, however, in which H versicolor had greater sensitivity to lower frequencies. This difference was supported by the observation of larger hair cell nuclei in the auditory sensory organs of H versicolor. Tuning at the midbrain was identical between the two species, suggesting that increased cell size biases the tuning of hair cell distortions more than their spectral sensitivity. Alternatively, a compensatory mechanism could prevent the lower tuning of hair cells from being expressed in the brain of H versicolor. Either explanation could involve selection to keep the tuning of hearing matched to the frog's conspecific advertisement call.

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Although the European flora belongs to the best explored at the global scale, still there are several largely neglected plant groups, which may surprise by marked variation. One of these groups is Urtica dioica s. l., consisting of vaguely described taxa (microspecies / subspecies) with indefinite distribution. The most important source of variation in U. dioica s. l. is probably polyploidy (2x, 4x; x = 13). The complex comprises an ubiquitous tetraploid cytotype (U. dioica s. str.) and several obscurely defined relict 2x taxa. The cytogeographical analysis through Europe (770 populations / over 3 200 individuals) revealed marked distribution pattern of U. dioica s. l. cytotypes. We identified 106 diploid populations (13%) and 633 (82%) tetraploid populations. For the first time we detected triploid and pentaploid level (from mixed populations). Prevailing tetraploid U. dioica s. str. is predominantly synanthropic, whereas diploid taxa strictly occur in primary and relict habitats (primarily alluvial forests, tundra, Mediterranean mountains). The analysis of the absolute genome size of individuals from U. dioica clade and other closely related taxa showed different values of 2x U. kioviensis (19 % higher than 2x U. d. subsp. subinermis) and 2x U. bianorii (33% higher than 2x U. d. subsp....