A construct comprising a CAG promotor, the ascidian Ciona intestinalis AOX (alternative oxidase) gene, a beta globin intron and a polyA site, plus an FLP site flanked neomycin resistance gene cassette were inserted into the locus. The neo cassette was removed through flp-mediated recombination. This creates an allele ubiquitously expressing an oxidase gene of a type not found in mammals. (J:238705)