Embryos derived from homozygous par^X1122 females raised at the restrictive temperature (25^oC) had hardly any space under the vitelline membrane at the posterior pole throughout the cleavage stage. Nuclear arrival in the posterior pole periplasm at the cleavage stage is delayed by 30 minutes compared with nuclear arrival in other regions. This is due to delayed migration of the nuclei. F-actin organisation is abnormal at the cleavage stage. par^X1122/Y male flies show a low lethality at the pupal stage.

At 28.5^oC, homozygous females have reduced ovaries due to abnormal egg chamber development; many chambers contain more than the normal number of sixteen cells and more than one oocyte. Few eggs reach the vitellogenic stage, those that are laid die before hatching. At 23^oC, homozygous females are fully viable and fecund, but 60% of their progeny fail to cellularise a complete blastoderm, due to asynchronous mitosis and defective nuclear migration in the late cleavage stage, and die soon afterwards. The remaining 40% survive to adulthood, but lack pole cells, and therefore have agametic gonads and are sterile. They also usually have a number of cuticle defects, which are graded postero-anteriorly in frequency. At 16^oC, homozygous females are partially fertile, 20% to 30% of their progeny are agametic and few cuticular defects are observed. Homozygous or hemizygous flies derived from any female have wing veins broadened into regular deltas at the junction with the wing margin.

Recessive temperature-sensitive female-sterile mutant. At 29^oC, homozygous females have small ovaries and abnormal egg chambers, the few eggs that are laid dying before hatching; at 23^oC par females are viable and fecund, but 60% of their progeny die without forming a complete blastoderm and the remainder form a blastoderm lacking in pole cells and develop into sterile adults with cuticular defects; at 16^oC, only 20-30% of the progeny of par females are agametic and few of these show cuticular defects. May act as a dominant enhancer of spl causing a spl phenotype in par spl/FM3 heterozygotes. A modifier Su(par) (mapping to right of v on X) decreases in a semidominant way the frequency of agametic flies (from 95-100% to 51-61%) and abdominal defects (from 26-49% to 5-14%) (Thierry-Mieg, 1982). The temperature-sensitive period is restricted to the mother's lifespan and the frequency of progeny defects is independent of the genotype of the zygote. The mutation interacts zygotically in trans with loci in the neighboring regions 3A2, 3A3, 3C1-2, 3C4 and 3C6-8. When z^a and/or w^a (wild-type eye color) are combined with par, a zygotic semidominant temperature-sensitive interaction takes place resulting in z^a par heterozygotes that are brown-eyed and z^a par w^a heterozygotes that are white-eyed. Interactions between par and N are also reported (Thierry-Mieg, 1982) such as the zygotic dominant suppression of Notch wing in par N⁺/par⁺ N^- females (the Notch mutants being Df(1)N-8 and Df(1)N-264-105 but not N^264-69, a point mutant). An interaction between par and a deficiency for 3A2 results in almost complete sterility in females with a paternal par X and in aging females with a maternal par X.