The effect of accessory chromatin on chiasma distribution in maize.

From an analysis of metaphase I bivalent configurations in Zea mays L. it was possible to determine the effects of two supernumerary elements on chiasma formation. Both the B chromosome and abnormal chromosome 10 increased chiasma frequency. In addition to enhancing total exchanges, both elements caused a redistribution of chiasmata from distal to more proximal locations.