About 80% of homozygous animals derived from heterozygous parents eclose, although subsequent generations show further decreased viability, probably due to decreased levels of maternal JIL-1 product. Only 8% of embryos derived from JIL-1^z2/JIL-1^EP3657 females mated to wild-type males hatch, of those larvae that hatch, 58% survive to pupation, and of those that survive to pupation 95% eclose. 94% of embryos derived from wild-type females mated to JIL-1^z2/JIL-1^EP3657 males hatch, and of those larvae that hatch, 95% survive to pupation. 87% of embryos derived from JIL-1^z2/+ females mated to JIL-1^z2/JIL-1^EP3657 males hatch, suggesting that some embryos with the JIL-1^z2/JIL-1^z2 or JIL-1^z2/JIL-1^EP3657 genotype can survive embryogenesis if provided with normal maternal JIL-1 product. No JIL-1^z2/JIL-1^z2 progeny survive to eclosion and the number of surviving JIL-1^z2/JIL-1^EP3657 adults is about half that of comparable sibling classes. Homozygous ovaries are moderately decreased in size compared to wild-type ovaries. In 88% of homozygous males, the A6 sternite is covered by one or more large bristles, indicating a transformation of A6 to the more anterior A5 segment. 93% of JIL-1^z2/JIL-1^EP3657 males have ventral sternite bristles on the A6 sternite, indicating a transformation of A6 to the more anterior A5 segment.

The hatch rate of homozygous embryos produced by homozygous parents is as low as 4-7%.

Mutant larvae expressing JIL-1^EP3657 under the control of Scer\GAL4^elav-C155 have ISN neuron pathfinding defects.

Homozygous larvae (derived from heterozygous females) have an eclosion rate of 81%. The number of males eclosing is 73% that of females. Eclosed adults are fertile and able to produce offspring. The hatch rate of embryos derived from homozygous parents is only 4%. The number of males eclosing is 48% that of females. Embryos derived from homozygous parents show a range of phenotypes from embryos appearing wild type with regularly spaced nuclei to embryos where chromatin structure is completely disintegrated. In intermediate phenotypes, nuclei in various stages of fragmentation are discernible. Centrosomes are often seen to be separated from the nuclear remnants and in other cases aberrant and misaligned tubulin spindles are seen. The polytene chromosome banding pattern is relatively normal in homozygous third instar larvae. Perturbation of the male X chromosome is relatively more severe than that of the autosomes which are only subtly affected.