Long description: The expression of genes is based on stochastic processes, which lead to temporal fluctuations in the number of proteins of each gene. If such fluctuations become too large they can be detrimental to the fitness of an organisms, because most cellular processes are based on the precise interaction of proteins. This PhD thesis explores the role of post-transcriptional regulatory mechanisms in the control of stochasticity in gene expression, with a focus on microRNAs, common regulators in multicellular organisms. Bioinformatic data analysis, mathematical modeling and single cell expression experiments are used to analyze the conditions under which microRNAs can lead to the reduction of fluctuations in gene expression. The central insight of this thesis is that microRNAs can indeed reduce fluctuations for most genes and that they are likely used by organisms for this purpose, thus ensuring precision to gene expression during development and the maintenance of the adult body. Der Expression von Genen liegen stochastische Prozesse zu Grunde, die zu Fluktuationen in der Menge von Proteinen eines jeden Gens führen. Zu starke Fluktuationen in Proteinmengen können für Organismen schädlich sein, da die meisten zellulären Prozesse auf der präzisen Wechselwirkung von Proteinen beruhen. Diese Dissertationsschrift |