Question

you grow E.coli that have a mutation in their Operator gene (O) so that the operon is constitutively active. what would happen when this mutant is grown in media that contains glucose, but not lactose? select all answers!!

A- the repressor would change shape

B- the repressor would bind the operator

c- the structural genes would be transcribed

D- RNA polymerase would bind the promoter

Answer 1

C and D

In the normal condition, repressor is bound to operator and prevents RNA polymerase from transcribing the Operon. This is switched off condition of lac operon.

In the question it is given that there is the mutation in the operator region. It means repressive won't be able to bind to operator. The Operon will never be switched off. Therefore there will be a constitutive expression of the Lac Operon.

Constitutive expression means the structural genes would be transcribed always. The transcription of these genes will never stop. The presence or absence of lactose does not matter.

There is no repressor on the operator. Therefore RNA polymerase will easily transcribe the Operon.

To summarise, mutation in the operator region will lead to constitutive expression. The Operon will be always with all irrespective of the presence of lactose.

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