ZsGreen transgene. (A) The transgene construct contains a chicken β-actin promoter with a CMV enhancer element followed by a chimeric intron. The floxed-STOP region contains loxP sites flanking 3 tandem SV40 polyadenylation signal sequences. Downstream of the floxed-STOP cassette is the ZsGreen gene sequence (originally derived from a Zoanthus sp. reef coral) followed by a bovine growth hormone polyadenylation signal. Upon Cre recombinase-mediated recombination, the loxP sites are recombined resulting in the excision of the 3 tandem SV40 polyadenylation signals. This event allows expression of the ZsGreen gene. (B) PCR amplification to demonstrate removal of the floxed STOP region from the ZsGreen-containing transgene. Lane 1: ZsGreen transgenic animal; Lane 2: NCre transgenic animal; Lane 3: double transgenic animal. Upper panel: results of amplification with primers flanking the floxed STOP region. Lower panel: results of amplification with primers that detect the Cre recombinase gene. A molecular size standard is shown to the left of the image. For reference, the uncropped image is included as Fig. S1.