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The core promoter is the ultimate target of all transcriptional regulatory processes. The recently discovered diversity of core promoters and basal transcription factors suggests a regulatory role in differential gene expression. However, the direct contribution of the core promoter remains poorly understood. I investigated core promoters and their putative role in differential gene regulation using the zebrafish embryo as an in vivo model system. To analyse the functional requirement for the general transcription factor TATA-box binding protein (TBP), a diverse set of promoters was tested for their TBP dependence. This analysis revealed a differential requirement of TBP for promoter activity. To further explore the roles of core promoters the ability of various core promoters to interact with tissue-specific enhancers was investigated. A high-throughput pipeline combining automated imaging with custom-designed software for registration of spatial reporter gene activity in thousands of zebrafish embryos was developed. The technology was applied in a large-scale screen analysing the tissue specific activities of 202 enhancer - core promoter combinations. A variety of interaction specificities observed suggests an important role of the core promoter in combinatorial gene regulation. Overall, these findings indicate that the core promoter significantly contributes to differential transcriptional regulation in the vertebrate embryo.

The thesis is concerned with the evolution of prices in market economies. In the first chapter we analyze price competition among firms with limited capacities in the framework of the classical Bertrand Edgeworth model. For this model it is well known that a Nash equilibrium in pure strategies may not exist. We discuss the nature of this non-existence result. While enlarging the strategy space to include non-linear strategies in general does not suffice for existence in the simultaneous move game, the possibility of reactions to competitors' actions in a dynamic context may restore equilibrium. In the remaining part of the thesis we analyze intermediation in frictional markets. When market participants are informed only imperfectly about potential trading opportunities, search and negotiations may prove costly. In such markets intermediaries by publicly quoting prices can help to reduce the transactional costs of exchange. In chapter two we analyze the case, in which intermediaries have access to an information technology which informs the full market. We characterize equilibrium. The inability of market participants to coordinate market participation is reflected in a large variety of subgame perfect Nash equilibria. Using a refinement criterion we find that high valuation traders typically trade with intermediaries, while low valuation traders engage in search. Moreover, price competition among several intermediaries yields Walrasian outcomes. Nevertheless, the market exhibits the features of a natural monopoly. In chapter three we relax the assumption concerning the information technology. An intermediary's choice of an information network determines the size of his clientele and hence the probability of trading. In this case the size of the information network is viewed as a quality attribute by market participants and imperfect price competition among intermediaries obtains. We characterize the industrial structure of those markets as natural oligopolies. Consequently, there is no convergence to a fragmented industrial structure as the economy grows large. Still, as the largest competitors are of roughly equal size equilibrium allocations tend to be fairly competitive.

Since the mid-2000s, the production of the pseudo-cereal quinoa (Chenopodium quinoa) for export has increased due to growing demand in the United States and Europe. To meet demand, many of those living in the Bolivian high plateau or altiplano have transitioned from traditional livelihood strategies to commercial quinoa production oriented at the international export market. The following looks at how Bolivians living in the community of Pampa Aullagas have adapted to commercial production by looking at three vignettes of different actors living in the community. Looking at traditional agropastoralists, teachers, and modern producers, this thesis seeks to understand the nuances and complexities associated with integration into the global export market.