Teratology and the development of pattern in Drosophila

Matheson, Alastair (1991). Teratology and the development of pattern in Drosophila. PhD thesis The Open University.

Abstract

This study investigates the developmental effects of permeabilisation, and subsequent physiological perturbations, on the embryo of the fruit fly Drosophila melanogaster, an organism studied predominantly by genetic techniques. A variety of abnormal syndromes, elicited by specific treatments and at specific stages of development, are investigated. Their implications for pattern formation in Drosophila, and their relationship to the genetic organisation of the system, are discussed.

Among the principal conclusions of the study are that the regulation of size and the organisation of the terminal regions are critically related to cell-state, in a stage-related fashion; that specific regions of physiological sensitivity are associated with the organisation of the anteroposterior pattern; and that dorsoventral pattern formation appears to pass through specific sensitive periods, in which a variety of specific factors play important but subtly differing roles. Further phenotypes are also investigated, which cast light on the obscure mechanisms involved in the co-ordination of the anteroposterior and dorsoventral axial systems. The results as a whole are used to construct a picture of the dynamic cellular organisation of early insect embryos and discussed in an evolutionary context.

The principal techniques used in this study are teratological: they make deductions about the early organisation of pattern from the range of aberrant final forms generated by developmental shock. The role and status of this methodology in modem embryology are ambiguous, reflecting both the emergence of more forensic analytical techniques, and deep philosophical dilemmas bound-up with the history of ontogenetic studies. This history is explored in detail to reveal the theoretical problems still facing the science.The value of teratology is finally reconsidered, with regard both to theoretical issues, and in the light of the practical studies carried out for this thesis.

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