LacZ expression in the JB6 host cell line. The murine keratinocyte cell line JB6 was transfected with a FRT flanked lacZ-Zeocin expression cassette. Clone JB6-pFRTLACZeo-7 was chosen for single genomic integration of the cassette and high β-galactosidase expression. a ELISA measurement of the rate of expression of β-galactosidase in chosen cell clones. Clone JB6-pFRTLACZeo-7 is indicated as a grey bar. b Formaldehyde fixated JB6-pFRTLACZeo-7 cells dyed with X-Gal.