The exons (and intervening small introns) that encode the mature robo1 protein have been replaced with a single exon encoding full length robo3 tagged with Tag:HA. The robo1KO.robo3 allele represents the loss of the robo1 open reading frame at the endogenous robo1 locus, while the robo3robo1.HR.Tag:HA allele represents the mature robo3 protein tagged with Tag:HA that is expressed under the control of the robo1 regulatory sequences in place of robo1.
robo1KO.robo3, robo3robo1.HR.Tag:HA has viable phenotype
robo1KO.robo3, robo3robo1.HR.Tag:HA has fertile phenotype
robo1KO.robo3, robo3robo1.HR.Tag:HA has larval longitudinal connective phenotype
robo1KO.robo3, robo3robo1.HR.Tag:HA has pCC neuron phenotype
Fas2-positive longitudinal fascicles of stage 16 roboKO.robo3 robo3robo.HR.T:Ivir\HA1 double homozygous embryos show midline crossing defects that are qualitatively and quantitatively similar to those seen in robo mutant embryos (Fas2-positive longitudinal fascicles extend across or along the midline in 99.2% of segments). In stage 13 roboKO.robo3 robo3robo.HR.T:Ivir\HA1 double homozygous embryos, the pCC axons project aberrantly across the midline, as occurs in robo mutant embryos.