Meiotic chromosome segregation occurs properly and is completed in the absence of fs(1)Ya function in unfertilised eggs.

Two abnormal nuclear distributions are seen in unfertilised eggs from fs(1)Ya² females. 34% of eggs contain two diploid nuclei, which is never seen in wildtype eggs. 14% of eggs have one diploid nuclei and two haploid nuclei. Of this latter case, two subtypes are observed. In one type, meiosis II has been completed but the central two nuclei, products of a separate meiosis II spindle, subsequently associate. In the other type, meiosis completes normally but subsequently two resulting haploid meiotic products associate or fuse.

There is no differences in the distribution of meiotic stages observed of nuclei upon in vitro activation of unfertilised wildtype vs fs(1)Ya²-deficient eggs.

The majority of fs(1)Ya² mutant embryos show disrupted nuclear arrangements. In 52% of embryos the male pronucleus does not associate with a maternal nucleus. In 13% of embryos, the male pronucleus does associate with a maternally-derived diploid nucleus in a manner that is never seen in wildtype. 17% of fs(1)Ya² embryos are in various stages of deterioration with fragmented or dramatically decondensed nuclei and can not be analysed further. 18% of fs(1)Ya² embryos resemble controls, having a gonomeric nucleus with a haploid maternal content and haploid paternal content, and three haploid maternally derived nuclei.

Roughly 25% of unfertilised fs(1)Ya² eggs show cell-cycle asynchrony of nuclear chromatin, which is never seen in wildtype. This defect is also observed in a smaller proportion of mutant embryos.

DNA replication can occur in fs(1)Ya² embryos and eggs.

Females doubly mutant for gnu³⁰⁵ and fs(1)Ya⁶ or fs(1)Ya² are indistinguishable from the fs(1)Ya embryos in terms of nuclear morphology.

Mutant embryos arrest either with multiple abnormal nuclei or at the pronuclear stage, with fewer than four abnormally condensed nuclei, presumably derived from the sperm and female meiotic products. In unfertilized eggs, two rather than four nuclei that would go on to form the polar bodies form, and the two are of unequal size and may show different degrees of chromatin condensation. Post meiotic coordination between chromatin condensation and nuclear fusion is abnormal. Fusion into one nucleus eventually occurs but the chromatin looks abnormally condensed.

Following pronuclear migration, 77% +/- 12% of eggs from homozygous fs(1)Ya² females are arrested with their two pronuclei closely apposed. The DNA in these embryos appears uncondensed, suggesting that the pronuclei are blocked after migration, but before entering the first embryonic mitosis. When these embryos are incubated for longer, their pronuclear DNA disperses and is eventually degraded. The remaining 23% of embryos (escapers) can pass through this initial block and undergo further mitoses, but these mitoses are highly aberrant. Most of these escapers arrest as syncytial embryos, with the remaining 1% arresting as gastrulae.