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Modern high-throughput technologies like DNA microarrays are powerful tools that are widely used in biomedical research. They target a variety of genomics applications ranging from gene expression profiling over DNA genotyping to gene regulation studies. However, the recent discovery of false positives among prominent research findings indicates a lack of awareness or understanding of the non-biological factors negatively affecting the accuracy of data produced using these technologies. The aim of this thesis is to study the origins, effects and potential correction methods for selected methodical biases in microarray data. The two-species Langmuir model serves as the basal physicochemical model of microarray hybridization describing the fluorescence signal response of oligonucleotide probes. The so-called hook method allows to estimate essential model parameters and to compute summary parameters characterizing a particular microarray sample. We show that this method can be applied successfully to various types of microarrays which share the same basic mechanism of multiplexed nucleic acid hybridization. Using appropriate modifications of the model we study RNA quality and sequence effects using publicly available data from Affymetrix GeneChip expression arrays. Varying amounts of hybridized RNA result in systematic changes of raw intensity signals and appropriate indicator variables computed from these. Varying RNA quality strongly affects intensity signals of probes which are located at the 3\' end of transcripts. We develop new methods that help assessing the RNA quality of a particular microarray sample. A new metric for determining RNA quality, the degradation index, is proposed which improves previous RNA quality metrics. Furthermore, we present a method for the correction of the 3\' intensity bias. These functionalities have been implemented in the freely available program package AffyRNADegradation. We show that microarray probe signals are affected by sequence effects which are studied systematically using positional-dependent nearest-neighbor models. Analysis of the resulting sensitivity profiles reveals that specific sequence patterns such as runs of guanines at the solution end of the probes have a strong impact on the probe signals. The sequence effects differ for different chip- and target-types, probe types and hybridization modes. Theoretical and practical solutions for the correction of the introduced sequence bias are provided. Assessment of RNA quality and sequence biases in a representative ensemble of over 8000 available microarray samples reveals that RNA quality issues are prevalent: about 10% of the samples have critically low RNA quality. Sequence effects exhibit considerable variation within the investigated samples but have limited impact on the most common patterns in the expression space. Variations in RNA quality and quantity in contrast have a significant impact on the obtained expression measurements. These hybridization biases should be considered and controlled in every microarray experiment to ensure reliable results. Application of rigorous quality control and signal correction methods is strongly advised to avoid erroneous findings. Also, incremental refinement of physicochemical models is a promising way to improve signal calibration paralleled with the opportunity to better understand the fundamental processes in microarray hybridization.

Errata inserted. / Bibliography: leaves 98-120. / x, 120, [4] leaves, [13] leaves of plates : ill. ; 30 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / This study is concerned with the identification of genes related to the very early stages of meiosis when homologous pairing occurs. A cDNA library is prepared at the premeiotic interphase and prophase stages of meioses. Differential screening is used to identify and select clones showing preferential expression in anthers at early meiosis. Two selected clones are chosen for further analysis and to investigate a possible role in chromosome pairing. / Thesis (Ph.D.)--University of Adelaide, Dept. of Plant Science, 1997

vii, 252 leaves : ill., photos., tables ; 30 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / Thesis (Ph.D.1979)--University of Adelaide, Dept. of Agronomy, 1978

The hybrids of three members of the viatica group of morabine grasshoppers from Kangaroo Island, South Australia, were studied. These members of the viatica group, which are primarily distinguished by their chromosome complements, have contiguous distributions. Grasshoppers collected from three narrow zones of overlap were studied cytologically. Breeding experiments were also conducted. The results of these studies indicate that a number of different factors contribute to the narrowness of the zones.

Thesis (Ph.D.) -- McMaster University, 1999. / Includes bibliographical references. Also available via World Wide Web.

Thesis (Ph. D.)--University of Oregon, 2007. / Typescript. Includes vita and abstract. Includes bibliographical references (leaves 201-241). Also available for download via the World Wide Web; free to University of Oregon users.

Diss. (sammanfattning) Uppsala : Uppsala universitet, 2006. / Härtill 5 uppsatser.

Thesis (Ph. D.)--University of Adelaide, Dept of Horticulture, Viticulture and Oenology, 1997. / Copy of author's previously presented paper inserted. Includes bibliographical references (leaves 187-218).

Thesis (Ph.D. 1979) -- University of Adelaide, Dept. of Agronomy, 1978.