The following hypothetical genotypes have genes A, B, and C corresponding to lacI, lacO, and lacZ, but not necessarily in that order. Data in the table indicate whether -galactosidase is produced in the presence and absence of the inducer for each genotype. Use these data to identify the correspondence between A, B, and C and the lacI, lacO, and lacZ genes. Carefully explain your reasoning for identifying each gene.
Genotype β-Galactosidase Production
Inducer Present Inducer Absent
1. A⁻B⁺C⁺⁻ + +
2. A⁺B⁺C⁻ + +
3.A⁻B⁺C⁺/A⁺B⁺C⁺ + +
4. A⁺B⁺C/A⁺B⁺C⁺⁻ + –
12. Gene Regulation in Prokaryotes
Lac Operon