Balancing the checks: surveillance of chromosomal exchange during meiosis.

During meiosis, numerous DSBs (double-strand breaks) are induced along the genome which are processed via several steps into crossovers. Crossovers ensure the faithful segregation of homologous chromosomes during meiosis I. Although required for faithful chromosome segregation, DSBs pose a severe hazard to genome integrity. Chromosome segregation in the presence of persisting DSBs can result in loss or missegregation of entire chromosome arms and in the formation of aneuploid gametes, conditions frequently associated with birth defects, still births and cancer susceptibility in offspring. Co-ordination between chromosomal exchange and meiotic cell-cycle progression is achieved via a surveillance mechanism commonly referred to as the recombination checkpoint. Both components of the mitotic DNA damage checkpoint as well as meiosis-specific functions contribute to this highly conserved surveillance system.