The lacz and lacy genes are transcribed when: glucose levels are high and lactose levels are low. lactose is absent and glucose levels are high. glucose levels are low, regardless of the level of lactose in the cell. lactose is present, regardless of the level of glucose in the cell. lactose is present and glucose levels are low.

lactose is present and glucose levels are low

Explanation:

Lactose operon or lac operon  (includes lacZ and lacY genes) is found in some bacteria and the products of its genes are involved in lactose metabolism. So, this operon is active (genes are transcribed) when lactose is present and glucose is absent. The operon is regulated by the lac repressor which acts as a lactose sensor and catabolite activator protein (CAP) which acts as a glucose sensor.

When there is lactose (in the form of allolactose) lac repressor detects it and stops being repressor. This enables transcription.

CAP detects glucose (via cAMP) and activates transcription when glucose levels are low/

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