CRISPR/cas9 genome editing used guide RNAs to target intron 1 of the Gt(ROSA)26Sor locus. Oligonucleotide donor DNAs were created encoding a duel landing pad flanked by the heterologous attP attachment sites - specifically a 48 bp Bxb1 attP-GT sequence, a 240 bp spacer of native Gt(ROSA)26Sor sequence and a 48 bp Bxb1 attP-GA sequence. (J:322700)