Lac Operon

Key Questions

  • Answer:

    removal of Lactose causing the repressor to be free and thus switching of the lac operon


    the working of the lac operon is explained very well in this video

  • Lac operon is an inducible system , it remains generally in off state , but in presence of Lactose it is switched on
    So Presence or absence of Lactose regulates operon functioning

  • Answer:

    The lac (lactose) operon is an operon that is essential for the transport and metabolism of lactose in E . coli as well as several enteric bacteria.


    The lac operon of E . coli is a cluster of three structural genes, encoding proteins involved in lactose metabolism and the sites on the DNA involved in regulation of the operon.

    Normally lac operon is turned off. The operon takes charge only when glucose levels are low. When glucose is unavailable the lac operon helps in the effective digestion of lactose. This is done through the activity of beta galactosidase. The operon uses a control mechanism that ensures the encoding of enzymes only when it is necessary. In the absence of lactose, the lac operon halts production of the enzymes encoded by the lac operon.

    This control mechanism causes the sequential utilisation of glucose and lactose metabolism and the sites on the DNA involved in the regulation of the operon.