Fig. 2. A large proportion of the upstream ribosomes drop off at UAAUG, the border between the coat and lysis genes. Escherichia coli JM109 cells harbouring the plasmid pL84Z (open circle, represents coupled lysis gene translation) or pCLZ (closed circle, represents the upstream coat gene translation) were grown at 37°C to an OD₆₆₀ of 0.15. β-galactosidase synthesis was induced by addition of IPTG (2 mM) at 37°C.