In the lac operon, what are the likely effects on operon gene transcription of the mutations described in a–e?
Mutation of consensus sequence in the lac promoter

Verified step by step guidance

1. Understand the role of the lac operon: The lac operon is a set of genes in E. coli that are involved in lactose metabolism. It is regulated by the promoter, operator, and regulatory proteins. The promoter is the site where RNA polymerase binds to initiate transcription.
2. Define the consensus sequence: The consensus sequence in the lac promoter is a specific DNA sequence that RNA polymerase recognizes and binds to. Mutations in this sequence can affect the binding efficiency of RNA polymerase.
3. Analyze the effect of the mutation: A mutation in the consensus sequence of the lac promoter is likely to reduce or eliminate the ability of RNA polymerase to bind to the promoter. This would decrease or prevent transcription of the operon genes (lacZ, lacY, and lacA).
4. Consider the impact on gene expression: If RNA polymerase cannot bind effectively, the operon genes will not be transcribed, even in the presence of lactose. This means the enzymes required for lactose metabolism will not be produced.
5. Summarize the outcome: The mutation in the consensus sequence of the lac promoter would likely result in a significant reduction or complete loss of operon gene transcription, leading to an inability of the cell to metabolize lactose efficiently.

Key Concepts

Lac Operon Structure

The lac operon is a set of genes in E. coli that are involved in the metabolism of lactose. It consists of three structural genes (lacZ, lacY, and lacA) and regulatory elements, including a promoter and an operator. The operon is activated in the presence of lactose and repressed when glucose is available, illustrating the principles of gene regulation in prokaryotes.

Promoter Consensus Sequence

The promoter consensus sequence is a specific DNA sequence recognized by RNA polymerase and transcription factors to initiate transcription. Mutations in this sequence can significantly affect the binding efficiency of RNA polymerase, leading to altered levels of gene expression. In the context of the lac operon, changes in the promoter can disrupt the transcription of the operon genes.

Transcription Regulation

Transcription regulation refers to the mechanisms that control the rate of gene transcription. In the lac operon, this regulation is achieved through the binding of repressor proteins and the availability of inducers like allolactose. Mutations affecting the promoter can lead to either increased or decreased transcription, depending on how they influence the binding of regulatory proteins and RNA polymerase.