Final answer:
In an E. coli culture with a nonfunctional lacI gene, the lac operon is always active, meaning the enzymes for lactose utilization are continually produced, regardless of lactose presence. However, lac operon expression is low when glucose is present because E. coli prefers glucose as an energy source. Only in the absence of glucose and presence of lactose does the operon fully activate.
Step-by-step explanation:
When E. coli is grown in a medium containing lactose, if the bacterial culture is irradiated with UV light causing the lacI gene to be nonfunctional, the effect on the activation of the lac operon would be significant. The lacI gene codes for the repressor protein that normally binds to the operator region and prevents transcription of the lac operon. If the lacI gene is nonfunctional, the repressor cannot bind, resulting in the lac operon being perpetually active, and the bacteria producing the enzymes necessary for lactose utilization even if lactose is not present.
However, the presence of glucose significantly affects this process. Although the lac operon would be derepressed without a functional lacI gene repressor, the operon is expressed at low levels as E. coli prefers glucose over lactose. If only lactose is present, and glucose levels are low, the CAP protein bound with cAMP can activate the transcription of the lac operon to ramp up the lactose utilization process.