Question

In the lac operon, what are the likely effects on operon gene transcription of the mutations identified below? Mutation of the lac I gene affecting the allosteric site of the protein.

1) Transcription is blocked.
2) Transcription is constitutive.

Answer 1

A mutation in the lac I gene affecting the allosteric site can either block transcription or result in constitutive transcription of the operon genes in the lac operon.

Step-by-step explanation:

In the lac operon, a mutation in the lac I gene that affects the allosteric site of the protein can have two likely effects on operon gene transcription:

1. Transcription is blocked: If the mutation prevents the repressor protein from binding to the operator, it will remain bound to the operator, blocking the transcription of the structural genes.
2. Transcription is constitutive: If the mutation prevents the repressor protein from binding to the operator altogether, transcription of the structural genes will occur constitutively, regardless of the presence or absence of lactose.

These effects on operon gene transcription can have significant implications for lactose metabolism in the cell.