This study is an analysis of the effects of formaldehyde, a chemical which is both recombinogenic and mutagenic, on white-ivory (wi) a highly mutable allele of the white locus of Drosophila. Formaldehyde is shown to significantly increase the reversion frequency of wi. The results of this investigation differ from earlier observations in three respects: (1) there is a positive correlation between RNA (ribonucleic acid) concentration and reversion frequency in the presence of formaldehyde, but reversion does not appear to be totally RNA dependent; (2) female germ cells are more sensitive than those of the male; and ( 3) a cluster of revertants has been recovered. These indicate that formaldehyde-induced wi reversion may involve a different mechanism than that proposed for formaldehyde-induced sex-linked lethals. Different mechanisms have been proposed to account for the induction of sex-linked lethals and for the increase in recombination. Formaldehyde-induced reversion of white-ivory follows the parameters of recombination.

Interest in the mechanisms of homeo domain specificity led to a screen that identified Drosophila proteins able to bind a consensus homeo domain site. One clone isolated in this screen produced no homeo domain and was selected for further characterisation as a protein with an unknown DNA binding domain and the potential to interact with homeo domain proteins on the DNA. This thesis describes the characterisation of the Drosophila gene dead ringer ( dri ) corresponding to this clone. Isolation of overlapping cDNA clones and sequence analysis allowed the identification of a complete open reading frame in the dri message that gave a predicted protein of 901 amino acids. Database searches and multiple sequence alignment revealed a widely conserved motif in the Dri sequence that is found in proteins from organisms as diverse as yeast, nematodes, flies and humans. Biochemical analysis of the properties of this conserved motif revealed that it could function as a DNA binding domain when expressed in a fusion protein. The in vitro specificity of the Dri DNA binding domain was determined by selection and sequencing of target sites. The Dri consensus site obtained was strikingly similar to that of the Qfo class of homeo domains, although the sequence and predicted secondary structure of the Dri DNA binding domain do not resemble a homeo domain. Analysis of the developmental expression pattern of dri showed a ubiquitous maternal deposit gradually refined to localisation in the mesoderm at germ band extension, then further restriction to a diverse set of tissues including the salivary gland ducts, parts of the gut and a subset of the central nervous system. The phenotype of P - element insertion and deletion mutations of dri were identified as causing embryonic lethality preceded by a disruption of the hindgut and loss of Dri expression in the ring gland. The identification of the novel, conserved DNA - binding domain in Dead ringer offers an explanation for the regulatory activity of several important related proteins and presents an opportunity to use the advantages of the Drosophila model system to clarify the role of these proteins in transcriptional control. / Thesis (Ph.D.)--Departments of Biochemistry and Genetics, 1996.

The present thesis is developed through four principal chapters. The first one provides a brief but rather exhaustive description of the context, with a global overview on the complex process of the embryogenesis in Drosophila Melanogaster. We amply focus on the three morphogenetic movements that will be numerically simulated, with particular emphasis on both the mechanical and the biological aspects that constitute the main peculiarity of each event. Also we propose a short review on the related previous works. The second chapter supplies the abstract tools for the analysis of the whole problem and points out the hypotheses that, for sake of simplicity, have been made. The gradient decomposition method is presented together with some interesting interpretations that better clarify the approach and put forward novel issues that have to be considered. By the Principle of the Virtual Power, we are able to write the mechanical equilibrium of the system which consists of the forces internal to the embryo domain and of the boundary conditions, such as the yolk pressure and contact with the vitelline membrane, that are essential for consistent results. A special concern is attributed to the choice of the constitutive law of the mesoderm that, from a biological point of view, may appear too simplistic. Here a Saint- Venant material is used in contrast with the Hyperelastic models found in literature; therefore a comparison between the two is proposed together with the advantages and the limitations of our study. Finally, we provide some simple examples that validate our model and support the exploited method. The third chapter can be divided into two parts. In the first one, by the parametrical description of the embryo geometry, we obtain the analytical formulations of the active deformation gradients for each morphogenetic movement according to the elementary forces introduced. Such expressions will be combined with the passive gradients in order to get the final deformation of the tissues. In the second part we interpret the results for each simulation. In particular, we provide a parametrical analysis for the simulation of the ventral furrow invagination, while for the germ band extension a comparison with experimental data is done. Furthermore we have been able to estimate the effects induced by the local deformations within the tissues; specifically, we have evaluated the magnitude of the pressure forces and the shear stress that may develop at long distance in the embryo when the active forces are applied in restraint regions. To conclude, we propose a collateral study on the influence of the global geometry of the embryo on the final results. Given the consistence of the results for the individual simulations, we have decided to test the concurrent simulation of the events, by two or three of them. In the last chapter, we show the results for a first essay for which we use the most intuitive method; it does not require in fact further manipulations of the analytical formulations previously obtained, but we simply couple together the active deformation gradients, following the chronological order of the movements. Although the method works well for the simulation of the two furrows, some drawbacks are detected when we introduce the germ band extension. Therefore we propose a new approach, more rigorous and appropriate, which allows to take into account some aspects so far put aside, but still significant for a realistic and complete reproduction of the different phases of the Drosophila gastrulation.

<p>In this project I have tried to obtain stable transformants of <em>Drosophila</em> melanogaster flies using electroporation. I have completed approximately 200 tests using different DNA concentrations, voltages and cuvettes, including a novel Petri dish cuvette which I developed and manufactured myself. I also developed new and more efficient procedures of egg collection and egg dechorionation. Although I was not  successful in obtaining true stable transformants, control experiments indicate that electroporation of DNA into embryos could be accomplished under the conditions used. The lack of stable transformants was probably due to failure of the electroporated DNA to integrate into the host genome. The reasons for why the DNA did not integrate was not further investigated in this study.</p>

The remodeling of the central nervous system (CNS) during metamorphosis in Drosophila melanogaster is a prime model system in which to study the genetic control of the sexual dimorphisms in the abdominal ganglion of the CNS. I have been using a P[tau-lacZ] enhancer trap line, 4.078, to label a segmentally repeated subset of abdominal motorneurons in order to assess the function of the sex determination hierarchy in controlling sex-specific development of the adult nervous system. In both the male and female larva there are 8 sets of these labeled abdominal motorneurons but only six sets in males and five sets in females survive in the adult. When this P[tau-lacZ] reporter construct is placed into a doublesex (dsx) mutant background, all 8 sets of these labeled abdominal motorneurons survive in both male and female adults. These results strongly suggest that dsx plays a role in the sex-specific survival of larval neurons that have functions in the adult. During the construction of mutant strains containing the sex determining genes transformer (tra) and transformer-2 (tra2), a genetic interactor was discovered in the P[tau-lacZ] 4.078 line. Female flies heterozygous for either tra or tra-2 alleles and the P[tau-lacZ] 4.078 developed with masculinized external and internal sex-specific structures. The external sex-specific structures, such as the genitalia, and ventral muscles are dependent on dsx gene function and a dorsal sex-specific muscle is dependent on fruitless (fru) gene function. From standard genetic crosses, I have characterized and demonstrated that the genetic interaction is linked to the P-element insertion site, which maps to the 85-87 region on the right arm of the third chromosome. By genetic analysis, this new genetic interactor appears to interfere with the tra and tra2 regulated female specific functions of both dsx and fru, potentially by reducing the female-specific splicing of the primary transcripts of the genes dsx and fru. To test the possibility that this newly described genetic interactor was allelic to a known gene, B52, that maps to the same region of the chromosome and alters dsx splicing, complementation tests were conducted which showed that the P[tau-lacZ] is not allelic B52. Additional phenotypes were observed in the crosses that first detected the interaction, suggesting that this newly described locus may affect other gene functions as well. Among the phenotypes observed were XX intersexes, male-female gynandromorphs (XX//XO mosaics), and non-disjunction events evident as XO males and XXY females. This new locus may represent a new member of the family of genes that influence regulated splicing events. / Graduation date: 1999

In Drosophila melanogaster, two chromosome-specific targeting and regulatory systems have been described. The male-specific lethal (MSL) complex supports dosage compensation by stimulating gene expression from the male X-chromosome and the protein Painting of fourth (POF) specifically targets and stimulates expression from the heterochromatic 4(th) chromosome. The targeting sites of both systems are well characterized, but the principles underlying the targeting mechanisms have remained elusive. Here we present an original observation, namely that POF specifically targets two loci on the X-chromosome, PoX1 and PoX2 (POF-on-X). PoX1 and PoX2 are located close to the roX1 and roX2 genes, which encode ncRNAs important for the correct targeting and spreading of the MSL-complex. We also found that the targeting of POF to PoX1 and PoX2 is largely dependent on roX expression and identified a high-affinity target region which ectopically recruits POF. The results presented support a model linking the MSL-complex to POF and dosage compensation to regulation of heterochromatin.

The persistence of sex is a recurrent conundrum in evolutionary biology because sex is costly. These costs may be accounted for by looking at the outcome of sex, namely that sex causes genetic mixing. Recombination is one of the processes by which sex causes genetic mixing; determining when recombination is advantageous may alleviate some of the costs of sex. The advantages of recombination are in the effects of recombination and the influences thereupon. The first experiment focuses on the effects of recombination on the mean fitness and variance in fitness. A second experiment examines the influences on recombination by addressing whether recombination is a general response to poor condition. Specifically, the impact on recombination rate of genotypes with variable fitness is investigated. Differing fitness effects are not correlated to recombination rates. Conversely, coincidence, a recombination related trait, is positively correlated with fitness.

The persistence of sex is a recurrent conundrum in evolutionary biology because sex is costly. These costs may be accounted for by looking at the outcome of sex, namely that sex causes genetic mixing. Recombination is one of the processes by which sex causes genetic mixing; determining when recombination is advantageous may alleviate some of the costs of sex. The advantages of recombination are in the effects of recombination and the influences thereupon. The first experiment focuses on the effects of recombination on the mean fitness and variance in fitness. A second experiment examines the influences on recombination by addressing whether recombination is a general response to poor condition. Specifically, the impact on recombination rate of genotypes with variable fitness is investigated. Differing fitness effects are not correlated to recombination rates. Conversely, coincidence, a recombination related trait, is positively correlated with fitness.

Thesis (M.S.)--West Virginia University, 2008. / Title from document title page. Document formatted into pages; contains vii, 110 p. : ill. (some col.). Includes abstract. Includes bibliographical references (p. 94-107).

Thesis (Ph. D.)--University of Washington, 2000. / Vita. Includes bibliographical references (leaves 70-81).