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Modern Genetic Analysis Chapter 14. Regulation of Gene Transcription Regulation of the Lactose System
Table 14-2. Synthesis of b-Galactosidase and Permease in Haploid and Heterozygous Diploid Strains Carrying I+ and I

|  | b-GALACTOSIDASE (Z) | PERMEASE (Y) |

Strain | Genotype | Noninduced | Induced | Noninduced | Induced | Conclusions

1 | I+Z+Y+ |  | + |  | + | I+ is inducible
2 | IZ+Y+ | + | + | + | + | I is constitutive
3 | I+ZY+/F IZ+Y+ |  | + |  | + | I+ is dominant to I
4 | IZY+/F I+Z+Y |  | + |  | + | I+ is trans-acting

NOTE: Bacteria were grown in glycerol (no glucose present) and induced with IPTG. The presence of the maximal level of the enzyme is indicated by a plus sign; the absence or very low level of an enzyme is indicated by a minus sign. (All strains are O+.)

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