A garden of forking paths: branching, switching and reversal in meiotic recombination

Meiotic recombination involves repair of double strand DNA breaks by homologous recombination to form crossovers and noncrossovers. Current models suggest that different mechanisms form these two products: noncrossovers by synthesis dependent strand annealing; COs by double Holliday junction formation and resolution. In testing these predictions, we found evidence for remarkable dynamism during meiotic DSB repair. This includes switching between repair templates and strand invasion by both DSB ends during both noncrossover and crossover recombination, and extensive branch migration by the Holliday junction intermediates that are CO precursors. I will discuss the mechanistic and regulatory implications of these findings.