Genetics - Theses
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ItemNo Preview AvailablePatterns of protein synthesis in larval and imaginal tissues of Calliphora : an analysis of gene activity during differentiation and development in a holometabolous insect(University of Melbourne, 1975)This study attempts to develop a logically consistent approach to the analysis of the genetic basis of complete metamorphosis in holometabolous insects,using the Australian brown blowfly, Calliphora stygia (Diptera), as the experimental organism. The following aspects of the problem have been examined: 1. Definition of the protein and enzyme spectra of selected larval and imaginal tissues during development. 2. Identification of the homologous gene products amongst various tissues with the view to establishing the uniqueness or overlap of gene readout in the series of tissues. 3. Identification of the times of synthesis of gene products as distinct from the duration of their occurrence leading to a definition of overall patterns of gene activities in the series of tissues. 4. Investigation of a specific model system for hormone action in vitro, namely with fat-body tissue and moulting hormone (MH). Current genetic models of insect metamorphosis have been examined in the light of the findings in this study of C. stygia.
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ItemNo Preview AvailableParthenogenesis, chromosomal polymorphism and morphological variation in Chironomids(University of Melbourne, 1973)Parthenogenesis, in the forms of arrhenotoky, deuterotoky, or thelytoky, is a quite common phenomenon in the animal kingdom. Thelytoky, in which females produce exclusively female progeny in the absence of genetic fertilization, is the most widespread and most mechanistically diverse form of parthenogenesis. It does not follow that thelytoky is the most common ; arrhenotoky, which only occurs in one rotifer, one arachnid and four insect orders (Hartl 1971), is probably the most successful form of parthenogenesis in terms of numbers, due mainly to the presence of over 100,000 species of hymenopterans, the vast majority of which are arrhenotokous. Thelytoky itself is present in a wide variety of forms. The mechanism for the maintenance of thelytoky may be automictic, in which at least the first meiotic division is normal, the chromosomes pairing at prophase and forming bivalents. The zygoid phase is restored by the restitution of anaphase I or metaphase II chromosome plates, fusion of second division products or endomitosis in cleavage nuclei. Alternatively the mechanism may be apomictic, in which meiotic features may be partly or wholly absent, the one or two maturation divisions being equational. Thelytoky may be complete, it being the only manner of reproduction; or it may be cyclical, where it alternates either regularly, or under the influence of environmental factors, with amphimixis or arrhenotoky. Thelytoky may also be either facultative or obligatory. Facultative thelytoky is the situation whereby reproduction is normally bisexual, however a percentage of eggs may develop without fertilization. Obligatory thelytokous forms produce all their offspring without genetic fertilization, reproduction can therefore never be bisexual. There are many thelytokous forms in which the eggs require penetration by the sperm of the same or related species before they develop. In this case, gynogenesis, the sperm makes no chromosomal contribution to the embryo, although there is a cytoplasmic contribution which may have some effect. In this chapter there are two main areas to be examined. The first is to investigate the cytology of two members of the chironomid subfamily Chironominae, Lundstroemia parthenogenetica and Lauterbornia sp. , and to compare them to other thelytokous forms with analogous maturation mechanisms, especially the members of the subfamily Orthocladiinae described by Scholl (1956, 1960). The second area is the discussion of the evolution and properties of thelytokous organisms. Most review articles tend to be limited to a broad presentation of the magnitude of the phenomenon (Oliver 1971), but also order the paper from the point of view of mechanism or animal groupings. Here the discussion is ordered from the point of view of the importance of various phenomena in the evolution and maintenance of thelytokous forms, e.g. hybridization, genetic and ecological considerations. This may not be a more systematic mode of presentation, but it seems to me to be more logical.
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ItemCytogenetic and evolutionary studies on macropathinae (gryllacridoidea : orthoptera)(University of Melbourne, 1970)The Gryllacridoidea are a very ancient and diverse assemblage. One of the four families included in it, the Sohizodactylidae, is confined to the Old World, while the other three, Stenopelmatidae, Gryllacrididae and Rhaphidophorinae, have a world-wide distribution. The latter family Is divided into the subfamilies Ceuthophilinae from North and Central America, Rhaphidophorinae mainly from Europe and Asia, and Macropathinae with a circum-antarctic distribution. Up to date, less than one hundred species of Macropathinae have been described, the majority of them from New Zealand and the surrounding islands. Fourteen species were described from the East and South of Australia including Tasmania and Flinders Island. A few species are from the Southern cone of South America while only one species has been described from Africa, in Cape Town. The majority of these species are forest inhabitants with nocturnal habits. During the day they hide in dark and humid places like hollow logo and or crevices. Caves and tunnels make a suitable place for then to hide in and reproduce. Their density in those places is sometimes remarkable and hence their fame of being mainly cave inhabitants. To collect these insects in forest is more difficult due to the fact that their populations are more scattered. The Macropathinae, like the remaining rhaphidophorids, are wingless. Their body length range from less than 1 cm. to nearly 5 cm. The length from the tip of the antennae to the hind tarsi reaches 45 cm in Gymnoplectron giganteum (Richards 1962). Information on chromosome numbers and chromosomal sex-determining mechanisms in gryllacridids other than Macropathinae is summarised in Table I. According to these data, the chromosome number varies widely from family to family and even within families. The majority of these papers deal with chromosomes at metaphase, information about the fine structure of chromosomes at prophase being very scarce. In the present study a survey on the chromosomes and terminal abdominal segments within Macropathinae was undertaken in order to find possible phylogenetic relationships within the subfamily. Sometimes it was unavoidable to enter the taxonomic field. In this respect, only the genera Miotopus, Pleioplectron and Weta wore fully treated. When new genera end species were involved, a brief, preliminary description was included. Nearly seventy species were investigated, about half of them being new species. About a dozen New Zealand new genera were discovered as well. Approximately fifteen hundred specimens were handled from which nearly four hundred were cytologically investigated. The description of this amount of species will undoubtedly take a long time and falls outside the scope of the present study, which must be only considered a preliminary report.
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ItemNo Preview AvailablePopulation genetics of chironomids : cytogenetics and cytotaxonomy in the genus Chironomus(University of Melbourne, 1966)
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ItemStudies of hybrids between members of viatica group of morabine grasshoppers( 1975-07)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.