Question

Describe how transcription in prokaryotic cells can be altered by external stimulation such as excess lactose in the environment.

a) Lactose inhibits the activity of transcription factors in prokaryotes.
b) Excess lactose activates repressor proteins binding to the operator.
c) Lactose induces the release of RNA polymerase from the promoter region.
d) Excess lactose prevents mRNA elongation in prokaryotic cells.

Answer 1

In prokaryotic cells, excess lactose acts as an inducer to inactivate the lac operon repressor protein, which allows RNA polymerase to transcribe genes necessary for lactose metabolism.

Correct option is c) Lactose induces the release of RNA polymerase from the promoter region.

Step-by-step explanation:

Transcription in prokaryotic cells can be altered by external stimuli such as excess lactose in the environment through the action of inducible operons like the lac operon. When lactose is present in the environment, it acts as an inducer, which inactivates the lac repressor protein. This prevents the repressor protein from binding to the operator site, allowing RNA polymerase to bind to the promoter and initiate transcription of the genes necessary for lactose metabolism. Therefore, in the context of the given options, excess lactose acts to deactivate the repressor, allowing transcription of the required genes, making option (b) incorrect and option (d) incorrect. Option (a) is not how lactose functions in this context, and option (c) misrepresents the function of lactose regarding RNA polymerase. The correct implication is that lactose induces the release of the repressor from the operator, which then permits RNA polymerase to transcribe the lac operon genes.