Final answer:
In the absence of both lactose and glucose, the lacZ gene will have low or negligible expression due to the repression of the lac operon by the repressor protein.
Step-by-step explanation:
To predict the level of expression for the lacZ gene in the given genotype and conditions (I+ O+ Z+ with no lactose and no glucose present), we need to consider the regulation of the lac operon in E. coli.
Under these conditions, the lac operon is not fully activated. In the absence of lactose, the repressor protein, which is a product of the I gene, binds to the operator site, effectively blocking transcription of the operon.
Since lacZ is a part of the operon, it will not be expressed significantly because the repressor prevents RNA polymerase from transcribing the operon, even though glucose is also absent. For maximal expression of the lac operon, lactose needs to be present, and glucose levels should be low or non-existent, which is not the case in this scenario.