Second chromosome nondisjunction is increased in both male and female homozygotes. A significant proportion of the diplo-2 exceptions are equational (approximately one third in males, 70% in females). The frequency of nondisjunction is relatively low; 0.6% in females and 1.3% in males, and is affected by environmental conditions (possibly humidity). Nondisjunction is not increased in heterozygous males or females, but there is a high frequency of equational exceptions in heterozygous females (compared to reductional exceptions), suggesting that mei-G871 may be semidominant.
Second chromosome nondisjunction is increased in homozygous males and females. There is no effect on sex chromosome, 3rd or 4th chromosome nondisjunction in males or females. Nondisjunction in the female may occur at the second meiotic division. The frequency of exceptional offspring varies greatly from experiment to experiment, suggesting that this mutant may be either a double mutant or a synthetic mutant.
A chromosome-specific but not sex-specific meiotic mutant; causes both reductional and equational nondisjunction of chromosome 2 in both males and females. In females, equational nondisjunction is independent of exchange, but reductional exceptions are primarily derived from non-exchange tetrads. In crosses of mei-G87 males to C(2)EN females, in which half the exceptions are recoverable, 6-10 exceptions per thousand eggs were recovered; in the reciprocal cross, in which all the diplo-2 exceptions are theoretically recoverable, there were 1-2 exceptions per thousand eggs. In primary spermatocytes, a low incidence of cases in which the chromatids of one pair of autosomes have separated are observed.
