Question

additional details were added for this assignment.
when is gene expression blocked in the lac operon system?
the repressor protein destroys the genes required to produce enzymes.
the repressor protein blocks the genes from making mrna.
rna polymerase begins transcribing the genes.
lactose binds to the repressor and changes its shape.

Explanation:

In the lac operon system, the repressor protein binds to the operator region. This binding physically blocks RNA polymerase from accessing the genes, thus preventing the genes from making mRNA. The repressor protein does not destroy genes (genes are stable DNA sequences). When RNA polymerase begins transcribing genes, gene expression is occurring, not blocked. When lactose binds to the repressor and changes its shape, the repressor can no longer bind to the operator, and gene expression is allowed (not blocked).

Answer:

The repressor protein blocks the genes from making mRNA.