Mutant for female meiotic segregation: 1.6% X chromosome exceptions from X/X females. 0.4% 4th chromosome exceptions from X/X females. 15.6% X chromosome exceptions from X/Bal females. 3.4% 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.