The FRT cassette present in the progenitor DroncKO.FRT.Dronc.WT.GFP.APEX2.FRT.Dronc.ΔCA.SunTag(Unk),Tag:HA,mCherry allele has been excised, allowing the mutated form of Dronc in which the CARD domain has been deleted and which also carries a C318A amino acid substitution in the catalytic residue (and which is tagged with SunTag(Unk), Tag:HA and mCherry at the C-terminus) to be expressed under the control of endogenous Dronc regulatory sequences.