Mutated strat exon 1 sequence has been reintroduced into the attP site present in TI{TI}stratCRISPR, resulting in a strat locus that encodes a protein carrying the C27A, N77A and D94A amino acid substitutions. Due to the reintegration event, an attL site is present upstream of exon 1, and a sequence cassette comprised of the following is present in intron 1: a loxP site, a w+* marker, an attR site, another loxP site, the Disc\RFPDsRed.3xP3.cUa marker that was present on the progenitor TI{TI}stratCRISPR chromosome, and a third loxP site.