Table 11-3: Synthesis of β-Galactosidase and Permease by the Wild Type and by Strains    Carrying Different Alleles of the λ Gene

 

 

β-Galactosidase (Z)

Permease (Y)

 

Strain

Genotype

Noninduced

Induced

Noninduced

Induced

Conclusion

1

I+ Z+ Y+

−

+

−

+

I+ is inducible

2

IS Z+ Y+

−

−

−

−

IS is always repressed

3

IS Z+ Y+/F′ I+ Z+ Y+

−

−

−

−

IS is dominant to I+

Note: Bacteria were grown in glycerol (no glucose present) with and without the inducer IPTG. Presence of the indicated enzyme is represented by +; absence or low levels, by −.