The exons (and intervening small introns) that encode the mature robo3 protein have been replaced with a single exon encoding full length robo1 tagged with Tag:HA. The robo3KO.robo1 allele represents the loss of the robo3 open reading frame at the endogenous robo3 locus, while the robo1robo3.HR.Tag:HA allele represents the mature robo1 protein tagged with Tag:HA that is expressed under the control of the robo3 regulatory sequences in place of robo3.
The eye photoreceptor cell projections in homozygous roborobo3.HR.T:Ivir\HA1 flies are indistinguishable from wild-type .
robo1robo3.HR.Tag:HA, robo3KO.robo1 has viable phenotype
All three Fas2-positive longitudinal fascicles form normally in robo3KO.robo roborobo3.HR.T:Ivir\HA1 homozygous embryos and Sema-2b-positive axons remain in the intermediate zone of the longitudinal axon pathway. There are no quantitative differences in Fas2-positive longitudinal pathway formation in robo3KO.robo roborobo3.HR.T:Ivir\HA1 homozygous embryos compared to wild type.
The characteristic robounspecified phenotype (crossing of the midline by Fas2-positive longitudinal axons) is not rescued if the embryos are also heterozygous for roborobo3.HR.T:Ivir\HA1.