LoxP sites were inserted upstream of exon 1 and in intron 1. This creates a conditional-ready allele with exon 1 floxed. Exon 1 contains the translation start site and its deletion would create a null allele. An FRT site flanked neomycin resistance gene cassette that was inserted into intron 1 was removed through flp-mediated recombination. (J:241413)