4. What molecule serves as an inducer of the lac operon?a) Lactosec) Allolactoseb)e) laclGlucosed) Galactose

The molecule that serves as an inducer of the lac operon is c) Allolactose.

Here's a step-by-step explanation:

1. The lac operon is a set of genes in bacteria that are used to metabolize lactose when glucose is not available.

2. The lac operon is usually turned off, or repressed, when glucose is present. This is because glucose is the preferred energy source for bacteria.

3. When lactose is present and glucose is not, the lactose is converted into allolactose.

4. Allolactose then binds to the lac repressor protein, which is produced by the lacl gene.

5. When allolactose binds to the lac repressor, it changes the shape of the repressor so it can no longer bind to the operator region of the lac operon.

6. This allows RNA polymerase to bind to the promoter region of the lac operon and begin transcription of the genes, leading to the production of enzymes that can metabolize lactose.

So, the molecule that serves as an inducer of the lac operon is allolactose because it is the molecule that actually binds to the lac repressor and causes it to release from the operator, allowing transcription to proceed.