Protein phosphorylation is now recognized to be one of the most important means of regulating protein activity. An approach was taken that was aimed at identifying new protein Serine/Threonine kinase genes in the fruit fly Drosophila melanogaster. Three of the kinases identified were chosen for molecular characterization: a Map kinase-activated protein kinase-2 homolog (DmMAPKAPK-2); a novel female germline specific kinase ( loki); and the homolog of the vertebrate cdk7 genes (Dmcdk7). Among those, Dmcdk7 was chosen for in depth molecular and genetic characterization. Cdk7 has previously been shown in vertebrate systems to phosphorylate and activate many different Cyclin-dependent kinases (Cdks) in vitro. However, conclusive evidence that Cdk7 could act as a Cdk-activating kinase (CAK) in vivo had remained elusive, and became even controversial. Adding to the controversy was the fact that in the budding yeast S. cerevisiae, CAK activity is provided by the CAK1/Civ1 protein which is unrelated to Cdk7. It was therefore proposed that the CAK activity of Cdk7 may be an in vitro artefact. In an attempt to resolve this issue null and temperature sensitive mutations of the Dmcdk7 gene have been created. The results obtained using these mutant alleles of Dmcdk7 demonstrate that cdk7 is necessary for CAK activity in vivo in a multicellular organism. It is shown that cdk7 activity is required for the activation of both Cdc2/Cyclin A and Cdc2/Cyclin B complexes, and for cell division. In addition to validate the function of Cdk7 as a bona fide regulator of the cell cycle, these results suggest that there may be a fundamental difference in the way metazoans and budding yeast effect a key modification of Cdks. Phosphorylation events at different sites (including the T-loop) are also known to be involved in stabilizing the Cdk7/Cyclin H dimer in vitro, and have been shown to occur in vivo. Surprisingly, the in vivo analysis of different phosphorylation mutant forms of DmCdk7 f

Bicaudal-C is a dominant maternal effect mutation which shows incomplete penetrance. Females are fertile and not all their progeny are affected. Those embryos which do not hatch show defects in their antero-posterior polarity, and give rise to bicaudal embryos which are duplicated for posterior structures. Twelve alleles of the genes have been phenotypically analysed. The penetrance of each allele has been determined and the phenotypes of embryonic defects such as mouth/head defect, bicaudal and uncellularized embryos classified and scored, in order to use this information to analyse these alleles at the cellular and molecular level. The bicaudal phenotype results from the mislocalization of the oskar and nanos RNA at the anterior end of the embryos. The gene also has a recessive phenotype which makes the females sterile. The phenotype is the result of specific defects in follicle cell migration. The alleles have been subdivided into two classes according to their phenotype: weak and strong. The gene encoding Bicaudal-C has been cloned and sequenced. It is expressed in the germline and appears to encode a member of the KH domain family of putative RNA-binding proteins.

Chromatin remodelers such as CHD1 (chromodomain, helicase/ATPase, DNA-binding domain) regulates histone dynamics and allows for higher order of chromatin compaction.CHD1 has been found to be important in fertility, wing development, and it colocalizes with elongating RNA polymerase II in Drosophila melanogaster. CHD1 is also important in embryonic stem cell pluripotency in mice and chd1 is the second most deleted gene in prostate cancer in humans. Furthermore, CHD1 suppresses the level of H3 dimethylated on lysine 9 (H3K9me2) and heterochromatin protein 1a (HP1a) to antagonize repressive chromatin. To complement these studies, I am seeking to determine the possible role of CHD1 on H3K9me2 and H3K56ac. Influence of CHD1 on histone dynamics is examined by using native chromatin immunoprecipitation at CrebA. We observed that H3K9me2 levels do not significantly increase over a single active gene in Drosophila salivary glands with the loss of CHD1, which implies CHD1’s effect might be only limited to heterochromatic regions. Additionally, I have preliminary evidence that the loss of CHD1 leads to an increase in the level of H3 acetylated on lysine 56, a mark of newly deposited histones. This evidence together with yeast studies provides a model for how CHD1 regulates nucleosome turnover.

The posterior cytoplasm of the Drosophila melanogaster egg and early embryo is very important because it forms pole cells which are the precursors to the germ cells found in the adult gonads. The posterior portion has been irradiated by many investigators to destroy these pole cells and record the types of effects the deletion has on the developing embryo. A St. Margarita Island strain of D. melanogaster contains a naturally occurring mutation on the X chromosome which affects the development of germ cells in the offspring. This mutation is a semi-dominant, maternal effect, temperature sensitive mutant. In this study female offspring from this strain were examined after having their X chromosomes subjected to 15 generations of selection for expression of agametic gonads. The agametic ovaries of these individuals were examined at the dissecting microscope, light microscope, and electron microscope levels and compared with normal ovaries of Oregon-R wild type females. The mutant ovaries examined contained normal mesodermal components but appeared to lack any developing stem cells or egg chambers. It was concluded that the mutant gene(s) morphological effects occur between the time the pole cells are incorporated into the posterior midgut of the embryo during gastrulation and the time they reach the adult gonad.

viii, 104 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.)--University of Adelaide, Dept. of Genetics, 1979

Diss. (sammanfattning) Umeå : Univ., 2004. / Härtill 3 uppsatser.

Thesis (Ph.D.)--University of Adelaide, Dept. of Genetics, 1998. / Errata is pasted onto back end paper. Includes bibliographical references (26 leaves).

Thesis (Ph.D.)--University of Nebraska-Lincoln, 2006. / Title from title screen (site viewed May. 20, 2008). PDF text: ix, 104 p. ; 547 K. UMI publication number: AAT 3298148. Includes bibliographical references. Also available in microfilm and microfiche formats.

Thèse (Ph. D.)--Université Laval, 2008. / Titre de l'écran-titre (visionné le 25 mars 2009). Bibliogr.

Thesis (Ph. D.)--West Virginia University, 2005. / Title from document title page. Document formatted into pages; contains v, 129 p. : ill. (some col.). Includes abstract. Includes bibliographical references (p. 118-129).