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

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

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 inhibited by a protein called the lac repressor, which is produced by the lacl gene.

3. When lactose is present in the environment, some of it gets converted into allolactose inside the bacterial cell.

4. Allolactose then binds to the lac repressor, causing it to change shape and release from the lac operon.

5. This de-repression allows the genes in the lac operon to be transcribed, and the bacteria can then metabolize the lactose.

So, the molecule that serves as an inducer of the lac operon is allolactose, because it's the presence of allolactose that ultimately allows the lac operon to be expressed.