Question: Suppose a bacteria had a mutated repress or protein that could not bind to the lac operator. How might this affect regulation of the Operon?

Jacinta Nzilani answered on 22 Jul 2025:

Hey,

🔍 What Happens If the Repressor Can’t Bind to the Lac Operator?

If a bacterium has a mutated lac repressor protein that cannot bind to the lac operator, here’s what happens:

🚫❌ Repression Fails
Normally, the lac repressor binds to the operator to block transcription of the lac operon when lactose is absent.

But if the repressor can’t bind (due to mutation), it can’t block the RNA polymerase. 😯

🧪 Result: Constitutive Expression
➡️ The lac operon stays ON all the time even when lactose is not present.

Genes like lacZ, lacY, and lacA will be transcribed continuously.

This leads to unnecessary production of proteins like β-galactosidase, wasting energy.

📘 Scientific Insight:
This type of mutation is called a constitutive mutation. It causes continuous expression of the operon regardless of environmental conditions.

🧠 Summary:
🦠 If the lac repressor can’t bind to the operator,
🔁 The lac operon will be expressed all the time.
⚠️ Even when lactose is absent, leading to energy waste.