The sequence just upstream of the stop codon was targeted for insertion of HA tag sequence with a gRNA (5'-GGGACCTACAGCAGAATAG-3') and an oligonucleotide donor, using CRISPR/Cas9 technology. The resulting allele has sequence coding for nine C-terminal haemagglutinin (HA) amino-acids inserted in-frame immediately upstream of the stop codon. (J:291761)