Mutant for female meiotic segregation: 20.9% X chromosome exceptions from X/X females. 65.2% 4th chromosome exceptions from X/X females. 52.5% X chromosome exceptions from X/Bal females. 53.6% 4th chromosome exceptions from X/Bal females. Segregation defective mutant. Causes primarily nondisjunction of meiotic chromosomes with only a low frequency of chromosome loss. Spindle abnormalities occur in only a small fraction ( <10%) of oocytes. Affects both exchange and non-exchange chromosomes.