Question

The lac operon can be regulated by two distinct methods. Which of the following statements are correct?The lac operon can be activated by the binding of allolactose to the repressor protein, releasing it from DNA and thereby allowing for transcription to occur.When glucose levels are low, the allosteric activator of the repressor protein dissociates, causing the repressor to release DNA and thereby allowing for transcription to occur.In response to low glucose levels, cAMP is upregulated; the binding of cAMP to the cAMP receptor protein triggers the activation of the operon.cAMP levels increase in response to low glucose levels and this secondary messenger allosterically binds to the repressor protein, causing it to release from DNA.

Answer 1

Answer:

• The lac operon can be activated by the binding of allolactose to the repressor protein, releasing it from DNA and thereby allowing for transcription to occur.

• In response to low glucose levels, cAMP is upregulated; the binding of cAMP to the cAMP receptor protein triggers the activation of the operon.

Explanation:

Lactose operon or lac operon  (includes lacZ, lacY and lacA 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 (or at low level). 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.