A CMV-chicken beta-actin hybrid promoter (CAG; also refered to as CBA in publication) with the cytomegalovirus immediate early enhancer linked to the beta actin proomoter and a chimeric intron of beta-globin and immunoglobin genes drives ubiquitous expression of the mouse cDNA preceeded by a floxed beta-gal-STOP-codon cassette. The pound symbol is used when no line is specified and/or lines are pooled.