This targeted knockout-first reporter allele with conditional potential (conditional-ready) was generated by electroporating ES cells with the EUCOMM vector PG00143_Z_7_G04 to insert a DNA sequence containing a FRT site; a lacZ cassette containing the En2 splice acceptor and a polyadenylation signal (p[A]); a loxP site; a promoter-driven neomycin resistance cassette with a p[A]; a second FRT site; and a second loxP site into the second intron and a third loxP site into the fourth intron of the mouse gene. (J:94077)