A linearized plasmid encoding the CAGGs promoter driving a codon optimized Flp recombinase (Flpo) and an IRES-puromycin sequence was introduced into JM8.F6 ES cells. Two clones were injected into 8-cell C57BL/6 albino embryos. One chimera showed germline transmission when crossed to C57BL/6 albino animals. (J:160215)