Exon 1 was targeted with sgRNAs (TAGGCTCTCTGCAATGGCTGAC, AAACGTCAGCCATTGCAGAGAG, TAGGGGTAAGCAGGTTGCTGA and AAACCTCAGCAACCTGCTTACC) and a donor plasmid containing a GFP gene and poly(A) signal sequence using CRISPR/Cas9 technology. This resulted an a knockout reporter allele where exon 1 is replaced with the GFP gene. (J:293325)