Question

What is negative regulation in lac operon?

Answer 1

Negative regulation in lac operon:

1. The molecule that inhibits transcription of the lac operon is a tetramer with four identical subunits called lac repressor.
2. lac repressor is coded by the lac l gene, located upstream of the lac operon, and has its own promoter.
3. lac l gene is not regulated so, a small amount of lac repressor is synthesized which binds to the operator and prevents transcription.
4. The absence of lactose repressor blocks the expression of the lac operon.
5. In the presence of lactose, lactose binds to the repressor as its affinity is high towards it.
6. So, the operator is free for transcription.