1.9% of expected mutant embryos hatch as first instar larvae. The latest observed stage of mutants is L1. Nerve cord length is 90% of embryo length. Midline guidance failure of repellence phenotype, evidenced by midline crossing, is severe.
The GMC-1 in mutants frequently (about 10%) divide symmetrically to generate two RP2s instead of an RP2 and a sib. The RP2 and aCC pCC and other neurons are occasionally misplaced within a hemisegment of the CNS of 13-hour or older mutant embryos, however in younger embryos these cells are not displaced and do not cross the midline or segmental boundary.