Final answer:
Glucose represses the utilization of lactose through low levels of cAMP and by inhibiting the transport of lactose via inducer exclusion. The correct options describing how glucose achieves this are (b) and (d).
Step-by-step explanation:
Glucose represses the utilization of lactose in glucose repression by several mechanisms. When considering which options describe how glucose represses the utilization of lactose, we can look at the behavior of the Lac operon in E. coli. This operon, a group of genes with a single promoter, is involved in the metabolism of lactose, and it is regulated based on the presence or absence of glucose and lactose.
(a) Glucose does not bind to the repressor instead of allolactose. This is incorrect because glucose itself does not bind directly to the repressor protein that regulates the Lac operon.
(b) The presence of glucose leads to a low level of cAMP. This is correct because when glucose is present, it leads to a decrease in the levels of cAMP, which is necessary for the binding of the CAP (catabolite activator protein) to the promoter, which in turn is required for the activation of Lac operon transcription.
(c) Glucose does not directly bind to the operator affecting how strongly RNA polymerase binds to the promoter. The regulation is indirectly affected by cAMP and CAP levels, not by direct binding of glucose to the operator.
(d) The presence of glucose inhibits the transport of lactose into the cell (inducer exclusion). This is correct because high levels of glucose lead to the prevention of lactose entry into the cells through a process called inducer exclusion.
Therefore, the ways in which glucose represses the utilization of lactose in glucose repression are options (b) and (d).