Question

Which of the following events would occur in ‘Lac–operon of E. coli when growth medium has high concentration of lactose?

• A. Structural genes fail to produce polycistronic $mRNA$
• B. Repressor protein binds to $RNA$ polymerase and prevents translation
• C. Repressor protein attaches to the promoter sequence and represses the operator
• D. Inducer molecule binds to repressor protein and $RNA$ polymerase binds to promoter sequence

Answer 1

The correct option is D Inducer molecule binds to repressor protein and $RNA$ polymerase binds to promoter sequence

Lactose (or allolactose) acts as an inducer in 'Lac' operon model. When lactose is present in high concentration in growth medium, it binds to repressor protein, which then fails to bind to operator gene. This results in $RNA$ polymerase binding to promoter region in gene and transcription of structural genes.