Exons 1 and 2 of Cyp3a57 were replaced with a hygromycin cassette containing a loxP site and subsequently inserting a neomycin cassette with a loxP site into intron 4 of Cyp3a59. Cre-mediated recombinase resulted in the deletion of Cyp3a57, Cyp3a16, Cyp3a41, Cyp3a44, Cyp3a11, Cyp3a25, and exons 1 to 4 and the promoter of Cyp3a59. (J:147112)