Abstract
Microsatellites, tandemly repeated sequences of period one to six basepairs, are genomic elements found in the genomes of all living species, from bacteria to humans. They exhibit a life cycle which can be decomposed into three major phases: an apparition and maturation phase, a mature dynamic phase, and a degeneration phase. This thesis focuses on the first phase, the microsatellite apparition.<br />This issue was investigated by analysing the complete human genome sequence. This requires extracting microsatellite loci from the sequence, using specific algorithms. However these available algorithms differs in detection method and efficiency. The first part of this thesis is dedicated to the comparison of some of the major algorithms of tandem repeats detection, and present an overview of their qualities and limitations.<br />Microsatellite birth essentially derived from transposable elements (TEs) or from mutation from any DNA sequence. The analysis of TE-mediated birth focuses on the role of Alu elements, using a comparative approach in three primate genomes. Mutation mediated birth is analysed though three different mechanisms: point mutation, DNA slippage and adjacent micro-duplication of a small number of nucleotides. A general model of microsatellite apparition is then proposed, suggesting a more complex apparition dynamic than was previously thought.