 The shuffling of genetic material during meiosis is driven by crossover events, which are controlled by the synaptonemal complex, SC. Mutations in Arabidopsis taliana that disrupt the SC lead to altered crossover patterns, which can be explained using a coarsening model. This model suggests that crossover precursors compete for a limited amount of a pro-crossover factor which then diffuses between the nucleus and cytoplasm before being exchanged at the sites of crossover. This article was offered by John E. Fozad, Chris Morgan, and Martin Howard.