Mutant for female meiotic segregation: 1.6% X chromosome exceptions from X/X females. 1.3% 4th chromosome exceptions from X/X females. 8.1% X chromosome exceptions from X/Bal females. 5.6% 4th chromosome exceptions from X/Bal females. Primarily affects achiasmate chromosome segregation. Causes high levels of chromosome loss with very little nondisjunction.