A TI{CRIMIC.TG4.0} DNA cassette has been inserted into γSnap1, in a coding intron, and is predicted to gene trap all annotated transcripts of the gene. The insertion may also affect the sei gene, since it is only 4 bp upstream of the 5' end of 1 of the 3 annotated transcripts of sei. The TI{CRIMIC.TG4.0} cassette was inserted using the CRISPR/Cas9 technique together with a donor plasmid to drive homology directed repair. The sgRNA sequence used to target the gene was: TTGTTGTCGATAGAAGACTTGGG. The homology arms of the donor plasmid used were designed such that there is a small gap between the 3' end of the 5' arm and the 5' end of the 3' arm, thus the insertion of the TI{CRIMIC.TG4.0} cassette is predicted to be accompanied by a deletion of 9bp of genomic sequence flanking the insertion site.