| Glucose | cAMP levels | RNA polymerase binding to promoter | Lactose | lac Repressor | Transcription of lac genes? | Lactose used by cells? |
|---|---|---|---|---|---|---|
| Present | Low | Absent | Absent | Active and bound to operator | No | No |
| Present | Low | Present, not efficient | Present | Inactive and not bound to operator | Low level | No |
| Absent | High | Present, very efficient | Present | Inactive and not bound to operator | High level | Yes |
| Absent | High | Absent | Absent | Active and bound to operator | No | No |