Both meiosis I and II proceed normally in heterozygous or hemizygous females. Heterozygous and hemizygous females are sterile; they lay normal numbers of phenotypically normal eggs that do not hatch. The majority of these eggs are fertilised, but the first cleavage division is normally never established. A small sperm aster forms in these eggs, as is seen in wild-type eggs, but in contrast to wild-type, this aster does not grow into a prominent sperm aster. The subsequent migration of the female pronucleus towards the male pronucleus does not take place. The first embryonic centrosome replicates once or twice, but the daughter centrosomes fail to separate. Concomitant with the failure of prominent sperm aster formation, the polar bodies migrate towards each other and fuse (first three and then all four polar bodies combine).

Female viability and male fertility are not reduced. The female and male pronuclei approach each other and almost fuse, however they do not divide. Phenotype is not fully penetrant so some embryos develop to the blastoderm stage.

Eggs of heterozygotes: sperm pronuclei may or may not divide but no fusion or further development.