How do operons regulate gene expression in bacteria and what happens when lactose is present?

How do operons regulate gene expression in bacteria and what happens when lactose is present?

• A. Lac operon is repressed by lactose; presence of lactose represses transcription.
• B. Lac operon is induced by allolactose binding to repressor, allowing transcription of lactose metabolism genes.
• C. Lac operon is constitutively active regardless of lactose.
• D. Lactose presence inhibits the promoter.

Answer: (B)