Is the synaptonemal complex a disjunction machine?

The chiasma has been recognized as a major feature of meiosis both visually and functionally for > 85 years. But its functional basis remains poorly understood. In interaction with the spindle, it generally mediates the ultimate distribution of homologues to opposite poles at meiosis I to yield correct disjunction. Its establishment depends upon the presence of a completed reciprocal recombination (crossover) event, but its maintenance from the time of crossover completion until anaphase I (a period of substantial extent) requires additional functions. Evidence for the nature of these functions, their relationship to synapsis and conjectures on their place in the evolution of meiosis are discussed here.