Sequence encoding FLP1 was adjoined to human ACTB promoter sequence, including 3 kb of promoter sequence and an 0.8 kb portion of exon 1. The promoter region drives expression in the germline. Recombinase activity is detected in a wide variety of tissues (spinal cord, heart, gonad, adrenal) as early as embryonic day 10.5. (J:78660)