Figure 6.

Maize knob neocentromeres and the maize karyotype, indicating some of the more common sites of heterochromatic knobs on the 10 chromosomes (Rhoades 1950). In the presence of a normal chromosome 10 (A), the knobs are inactive and lag behind the normal centromere at meiosis (inset). When the normal chromosome 10 is replaced by Ab(10), the knobs become neocentromeres. These neocentromeres bind the spindle microtubules in a lateral rather than an end-on manner and migrate towards the spindle pole in advance of the normal centromeres that remain active (B). Yellow indicates an active centromere or neocentromere.