Project Summary The general goal of the proposed research is to define the pathways and their mechanisms by which homologous recombination contributes to genome instability in somatic cells through events involving repeated DNA sequences. Using the budding yeast Saccharomyces cerevisiae as a model organism we will define the mutational signatures of multi-invasion-induced rearrangements, which are induced by a single Rad51-ssDNA filament simultaneously pairing with repeated DNA sequences on different chromosomes or locations on a single chromosome. The aims are designed to establish novel mechanisms and paradigms that are applicable to central questions concerning genomic stability and genome maintenance. We will establish novel mutational signatures caused by homologous recombination that will help to define the mechanism underlying such signatures found in humans, including cancer genomes. Moreover, our work will contribute to understanding the mechanisms underlying major processes that shape genomes during ontogenic development and evolution, including non-allelic homologous recombination, insertions, mutation showers (kataegis), double minute chromosome formation, and chromosome instability syndromes such as chromothripsis. The Specific Aims are: (1) Determine the genetic consequences of multi-invasion-induced genome rearrangements. and (2) Identify pathways that affect multi-invasions and the genome-wide search for homology. Both aims require the use of the table-top centrifuge requested in this application.