Mutant for female meiotic segregation: 2.1% X chromosome exceptions from X/X females. 0.5% 4th chromosome exceptions from X/X females. 9.8% X chromosome exceptions from X/Bal females. 1.4% 4th chromosome exceptions from X/Bal females. Shows high levels of X nondisjunction but low levels of 4th chromosome nondisjunction. Primarily affects achiasmate chromosome segregation.