LD2668 .T4 1962 P37

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Theoretical considerations predict that hybridization between plants with different breeding systems could potentially be a powerful evolutionary force but very few studies have been carried out to investigate hybridization among outcrossing and selfing species in natural populations. The objective of this thesis was to use G. urbanum and G. rivale, two freely hybridizing species with putatively different breeding systems, and study the processes that take place when the two different mating systems meet. To establish the extent of the morpholofical and genetic marker differences, the breeding system and levels of inbreeding depression in these two species, I examined reference populations from various locations in Great Britain using morphological (nine phenotypic traits) and genetic analyses of a long standing hybrid swarm between G. urbanum and G. rivale, the results revealed that the two parental species differed signigicanly in all nine traits measured and were clearly separated by 616 AFLP markers, of which 8% were species-specific. The breeding system analysis confirmed the highly selfing nature of G. urbanum and the outcrossing nature of G. rivale. No inbreeding depression was discovered in G. urbanum and very low levels in G. rivale. The AFLP analysis (203 loci) of the hybrid swarm showd that four distinct genetic groups can be distinguished (1) a parental G. urbanum life group (2) an F1 like group (3) a Backcross Rivale group and (4) a parental G. rivale like group. No Backcross Urbanum individuals were detected. Morphological data were hightly correlated with genetic data (Spearman Rank Order Correlation = 0.08,p<0.0001) but less informative as morphological data could not separate the Backcross Rivale samples from G. rivale. Analysis of seed progeny from the hybrid swarm showed that there were clear differences in the genotypic composition of the seed porgeny and the plants from which they were collected, revealing additional genetic classes such as Backcross Urbanum individuals which were not represented in the adult plant state. The Backcross Rivale parental group was the only one in which the average offspring position did not differ signigicantly from the mean parental psition in a PCO plot using 203 AFLP markers, indicating that this group might be reporductively isolated from other groups in the hybrid swarm. Taken together the results suggest that hybridization between G. urbanum and G. rivale results in the production of a range of genotypic and phenotypic classes, some of which are selected against. There is evidence for introgression between these two species, and tentative evidence for partial reporduction isolation of some hybrids suggestion that hybridisation between these outcrossing and selfing Geum species may represent a creative evolutionary force.

The purpose of this paper is to set forth the purpose of wheat hybridization. To do this properly it is necessary to know the history of hybridization of plants. Also to know some of the workers in this field and the hybrids produced by them. In the work at the Experiment Stations the various experimenters have discovered many interesting facts which it is necessary to know and understand. To thoroughly comprehend the work it is also necessary to do the actual processes of the work and to carry the hybrid through several generations and eventualy to the goal for which purpose the cross was made to attain.

The typical intermediate morphology of hybrids may result in their failure to utilize the same niches as their parents. However, the fitness consequences of the potentially intermediate life-history traits of hybrids have been given less scientific attention. In this study I aimed to investigate how life-history divergence in parental species affects the relative fitness of nestling hybrids resulting from crosses between collared (Ficedula albicollis) and pied flycatchers (F. hypoleuca). Previous studies showed that collared flycatcher nestlings beg more intensively and grow faster under good conditions, but are less robust against the seasonal decline in food availability compared to pied flycatcher nestlings. This life-history divergence between the species allows regional coexistence. To investigate whether the life-history divergence in flycatchers influences the relative fitness of nestling hybrids, I cross-fostered hybrid nestlings in aviaries into the nests of conspecific pairs and compared their performance. I found that the hybrids displayed intermediate growth rates between collared and pied flycatchers across the season. There might therefore be environmental conditions when hybrids perform better than purebred offspring with respect to growth and survival.

Functional inactivation of tumor susceptibility gene tsg101 leads to cellular transformation and tumorigenesis in mice. No genomic DNA deletion in TSG101gene in human cancer indicated TSG101 is not a typical tumor suppressive gene. TSG101 participates in the MDM2/p53 feedback control loop and the regulation of the cellular membrane trafficking. However, detail functional characteristics remains to be elucidate. In this study, we explored the tsg101 expression in adult mouse tissues from various organs using immunohistochemistry and in situ hybrid- ization. The results indicated that tsg101 expression was ubiquitous but in differential steady-state level in various cell types. The expression of tsg101 mainly found in epithelial cells¡Bsecretory cells and nerve cells. The second topic of this study was to characterize the phosphorylation status of TSG101 protein. Endogeneously expressed TSG101 and exogeneously expressed HA-tag TSG101 protein were purified by immunoprecipiation with #820 antiserum against TSG101, and were subjected for western blot analysis using anti-phosphoserine and anti-phosphothreonine antibodies. This experiment had confirmed that TSG101 protein contained both phosphoserine and phosphthreonine residues. In vitro kianse assay using GST-tag and his-tag TSG101 funsion proteins was exploited to investigate the kinase responsible for TSG101 phosphorylation. The results clearly indicated that cdc2¡BGSK3£] and PKC kinases could phosphorylate TSG101 fusion Protein, implying that the function of TSG101 might be regulated by the signaling involving these kinases.

Thesis (Ph. D.)--University of Queensland, 2002. / Includes bibliographical references.

No description available.

The presence of parasites in a population has an impact on mate choice and has substantial evolutionary significance. A relatively unexplored aspect of this dynamic is whether or not the presence of parasites increases the likelihood of hybridization events, which also have a significant role in ecological adaptation. One explanation of increased hybridization in some areas and not others is that stress from parasites results in selection for an increase of novel genotypes. Two swordtail species Xiphophorus birchmanni and Xiphophorus malinche maintain an active hybrid zone. The patterns of hybridization are unique in that they do not match up directly with expectations. We set out to test whether or not individuals can sense, using chemical cues, whether conspecifics in their immediate vicinity have high parasite loads and also whether this has an effect on mating and association behavior toward both conspecific and hybrid mates. Our hypothesis being that females will have greater association times with hybrid/heterospecific mates if conscpecifics are heavily parasitized. We found that females exposed to parasitized males had a weaker preference for conspecific odor than those exposed to unparasitized males, both relative to a water control and relative to hybrids. The empirical investigation described above is coupled with a historical and philosophical discussion of some of the issues surrounding the acceptance and understanding of the concept of hybridization. This discussion takes as its major themes: an analysis of the role that social views have on the formation of scientific hypothesis; the lag between epochal change in the scientific community and the assimilation of the consequences into social beliefs; the survival of hierarchical and teleological thinking in our concept of species and purity; and the failures of contemporary evolutionary theory to provide satisfactory explanations about the meaning and upshot of hybridization. Two specific misconceptions about hybridization are addressed. First, that hybridization clashes with the belief in kinds/types/species having separate and pure identities. Secondly, the teleological view that reads purpose into nature and places all instances of variation on a hierarchical scale; the top and bottom of which are determined by estimated closeness to the predetermined perfection of a type. < <

The unique spectroscopic properties of quantum dots (QDs) are of interest for application in intracellular studies of gene expression. QDs derivatized with single-stranded probe oligonucleotides were used to detect complementary target sequences via hybridization and fluorescence resonance energy transfer (FRET). As nucleic acid targets are not labeled within cells, a displacement assay for nucleic acid detection featuring QDs as FRET donors was developed. QDs conjugated with oligonucleotide probes and then pre-hybridized with labeled target yielded efficient FRET in vitro. Studies in vitro confirmed that displacement kinetics of pre-hybridized target was a function of the stability of the initial hybridized complex. Displacement was observed as reduction in FRET intensity coupled with regeneration of QD fluorescence. By engineering the sequence of the labeled target, faster displacement was possible. The QDprobe+target system was successfully delivered into cells via transfection. Although QDs with their cargo remained sequestered in endosomal vesicles, fluorescent properties were retained.