A minigene containing the coding sequence of the inserted gene with a C-terminal HA tag was coupled to genomic sequence containing the last three exons (3' part of exon 9 through entire exon 11) of the host gene. This combined sequence followed by a loxP-flanked neomycin resistance gene cassette was inserted at the ATG translation start site of the host gene. Subsequent cre-mediated recombination removed the neo cassette. Experiments confirm the functional expression of the inserted gene and knockout of the host gene. (J:234164)