The transgene construct comprises the following elements: the CAG promoter, A loxP site, a chloramphenicol acetyl transferase gene and STOP cassette, a second loxP site, the mCherry red fluorescent gene fused in-frame (via a Gly-Gly-Ser linker) with the mouse polo like kinase 4 cDNA, and SV40 poly(A) signal sequence. The construct was microinjected into the pronuclei of fertilized oocytes. This creates a conditional-ready allele where the inserted chimeric reporter-kinase sequence will only be expressed after cre-mediated excission of the floxed CAT gene. (J:198922)