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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

Genetic sex : a symbolic struggle against reality? : exploring genetic and genomic knowledge in sex discourses

Holme, Ingrid January 2007 (has links)
Genetic sex -the apparent fundamental biological cause of the two male and female human varieties- is a 20th century construct. Looking down the microscope, the stained chromosomes are concrete countable entities and lend themselves easily to genetic determinism. As the chromosome composition of a person is generally fixed at the time of conception, when a Y- or X-bearing sperm is united with the X-bearing egg, a person’s genetic sex is taken as permanent and unchanging throughout their life. Drawing upon gender theory as well as science and technology studies this thesis explores how our particular construction of the concept of ‘genetic sex’ relies on four features of biological sex (binary, fixed, spanning nature, and found throughout the body) and in addition proposes one unique feature, inheritance. The empirical research is based on an analysis of popular science books as well as two case studies of how genes relate to sex determination and development. The analysis of the metaphors used in these books and journal articles reveals how now, with genomic efforts to explore gene expression profiles, there is a shift away from seeing genes as having ‘responsibilities’ for determining phenotypes towards seeing them play a role along with other genes in genetic cascades where other factors such as timing can be incorporated. The analysis of genomic features such as imprinting and X-chromosome inactivation also provide evidence that such a change should be recognised. Rather than seeing sex in terms of fixed and static differences and similarities, current research offers new ways of conceptualising similarities and differences as dynamic and responsive to environment. This supports wider understandings of ‘biology’ as relying on the interactions between genetic processes, cellular environment, and tissue environment – in which the social physicality of bodies is important in forming and maintaining a person’s biology and genetic processes. Yet as the historical analysis of the shift between the one sex to two sex model indicates, it remains to be seen whether the social sphere will respond by incorporating this new evidence into the tacit, everyday understandings of sex or seek to maintain the binary and fixed relationship(s) between men and women by governing them as males and females.
2

Diversité et évolution chez Vitis vinfera L. de traits impliqués dans le syndrome de domestication et dans la biologie de la reproduction / Diversity and evolution of traits implicated in reproduction biology and in domestication syndrom in wild grape (Vitis vinifera ssp. sylvestris) and domesticated grape (Vitis vinifera ssp. sativa)

Picq, Sandrine 09 February 2012 (has links)
La domestication est un processus évolutif complexe au sein duquel les pressions de sélection exercées par l'Homme conduisent à des changements morphologiques et physiologiques importants qui permettent de différencier sans ambigüité les espèces domestiquées de leurs ancêtres sauvages. Les récentes études archéobotaniques, génétiques et génomiques sur différentes plantes annuelles telles que notamment, le maïs (Zea mays L.), le riz (Oryza sativa L.) ou la tomate (Solanum lycopersicum L.) ont considérablement fait progresser notre compréhension de la domestication des plantes. A la différence des espèces annuelles, la domestication des plantes pérennes, en particulier les espèces fruitières, reste énigmatique.Dans ce contexte, l'objectif de ce travail est de contribuer à la compréhension du processus de domestication d'une plante pérenne fruitière emblématique, la vigne (Vitis vinifera L.) à travers l'étude de la diversité et de l'évolution de deux caractères majeurs du syndrome de domestication : la forme du pépin et le système de reproduction. Nos travaux sur la morphologie du pépin appréhendée par la méthode des transformées elliptiques de Fourier ont révélé des relations significatives entre la forme du pépin, le statut taxonomique (sauvage – domestiqué), l'origine géographique des cépages et leurs liens de parenté corroborant les résultats d'analyses génétiques acquises antérieurement. D'autre part, le changement de forme du pépin se produisant au cours de la domestication serait intimement lié à l'augmentation de la taille de la baie due aux pressions de sélection exercée par l'Homme. Concernant la transition de la diécie vers l'hermaphrodisme opérée au cours de la domestication, l'analyse du polymorphisme de séquences du locus du sexe a révélé que les vignes domestiquées seraient les descendantes d'individus mâles capables de produire des baies. Le patron de diversité de ces mêmes séquences corrobore l'idée d'un événement de domestication majeur de la vigne dans le Proche Orient et témoigne de l'existence d'introgressions du compartiment domestiqué par le compartiment sauvage dans l'Ouest du bassin Méditerranéen. / Domestication is a complex evolutionary process in which, human selection pressures lead to great morphological and physiological changes that allow to differentiate domesticated species from their wild ancestors. Recent archaeobotanical, genetic and genomic studies of various annual crops such as maize (Zea mays L.), rice (Oryza sativa L.) and tomato (Solanum lycopersicum L.) have significantly advanced our understanding of plant domestication. However, the domestication of perennial plants, particularly fruit trees, remains poorly documented compared to the domestication of annual crop plants.In this framework, this work aims to contribute to the understanding of the domestication process of the emblematic perennial plant, the grapevine (Vitis vinifera L.) through the study of diversity and evolution of two major traits of the domestication syndrome: the seed shape and the reproductive system. Our work on seed shape based on the method of the elliptic Fourier transforms revealed significant relationships between seed shape, the taxonomic status (wild – domesticated), the geographic origin of cultivars and their parentage relationships, corroborating former results from genetic analysis. On the other hand, seed shape changes occurred during domestication seem to be linked to the increase of the berry size as the consequence of major human selection pressures. Regarding the transition from diecy to hermaphroditism to diecy operated during domestication, the analysis of sequence polymorphism in the sex locus revealed that domesticated grapevine would be the descendant of wild male individuals able to produce berries. The pattern of diversity of these sequences supports the hypothesis of the occurrence of a major domestication event in the Near East and testify of introgressions of Western European cultivars by local wild grapes.

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