The secret of safe reproduction

Sexual reproduction involves the formation of gametes – specialized cells containing half the genetic content of their parental cells. During meiosis, maternal and paternal chromosomes align and swap DNA segments, a process which requires programmed double strand breaks. Cells must guarantee at least one crossover per chromosome pair, but excessive double strand breaks can lead to deleterious DNA damage. How do cells balance these requirements? A new study from the Matos lab in Nature reveals a crucial mechanism involving Holliday junctions and the synaptonemal complex that ensures genetic diversity.