Exons 1-5, which contain the entire coding region of the gene, were replaced with a loxP site, the mouse Ace (angiotensin I converting enzyme (peptidyl-dipeptidase A) 1) promoter, the cre recombinase gene, a neomycin resistance gene cassette, and a second loxP site. After Cre-mediated self-excision in the male germline, a single loxP site remained in place of the gene. (J:126321)