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.

En Méditerranée, le corail rouge présente un important rôle écologique dans les écosystèmes benthiques de substrat dur. Les conditions environnementales, et notamment thermiques extrêmement contrastées que cette espèce subit sur l'ensemble de son aire de répartition, en font un modèle intéressant pour l'étude de l'adaptation locale. Dans un premier temps, nous avons confirmé que les différences d'expressions de gènes étaient maintenues au cours du temps, en absence de stress thermique chez des individus issus de profondeurs différentes à Marseille. Certains des gènes identifiés sont de bons candidats pour l'étude de l'adaptation locale et de forts arguments en faveur de la conservation de cette fonction chez les cnidaires. Afin d'identifier d'éventuelles bases génétiques de l'adaptation locale chez le corail rouge, nous avons mis en place un protocole d'échantillonnage de paires de populations `surface vs profondeurs' dans trois régions géographiques différentes suivi d'un séquençage via RAD-Séquençage. L'analyse de la structure génétique neutre indique une connectivité réduite entre les populations de surface et à fois populations de surface et les populations profondes qui pourrait limiter les capacités de recolonisation des populations les plus exposées aux pressions du changement global. Nous avons identifié un signal probable d'adaptation locale, sans qu'une convergence dans les gènes ou les fonctions candidats n'ait été observée. L'analyse de la structure génétique chez le corail rouge a conduit à l'identification de marqueurs génétiques du sexe. / The Mediterranean red coral has an important ecological role in Mediterranean benthic ecosystems and is submitted to major anthropic pressures because of its direct (exploitation) and indirect (attractivity for recreational scuba-diving) economical values. Because of the extremely contrasted thermal conditions it deals with along his range the red coral is an interesting model for the study of local adaptation. We first confirmed that gene expression differences were maintained along time, in absence of thermal stress in individuals from different depths in Marseille. Some of these genes were good candidates for the study of local adaptation and strong arguments supporting the conservation of this function in cnidaria.In order to identify potential genetic basis of the local adaptation in the red coral, we built a sampling design of pairs of `shallow vs deep' populations in three geographical regions and sequenced via RAD-Sequencing the corresponding individuals. The analysis of neutral genetic structure of the studied populations highlighted a limited connectivity of shallow populations with both shallow populations and deep populations that could counteract recolonization abilities of population the most exposed to global change. Several methodological obstacles have been met in the detection of loci under selection in such strongly structured species. By keeping in mind these potential biases, we highlighted a potential signal of local adaptation in Marseille and Corsica, without any convergence in candidates genes and functions. The analysis of the genetic structure of the red coral led us to the identification of sex genetic markers.