Question

Explain how a mutation in a promoter can affect gene expression.

Short answer

A mutation in a promoter can affect gene expression by either increasing or decreasing the efficiency of RNA polymerase binding, which directly impacts the rate of transcription. Higher or lower transcription levels can lead to too much or too little production of certain proteins, potentially causing diseases such as certain types of cancer.

Step-by-step solution

Understanding Promoters and their Role in Gene Expression

A promoter is a region on the DNA, usually located upstream (on the 5' end) to the gene it controls. It's where RNA polymerase binds to commence transcription. Transcription is the first step in gene expression, it's where the DNA sequence of a gene is copied into mRNA.

Knowing the Possible Impact of a Mutation in a Promoter

When a mutation occurs in the promoter region, it can cause the RNA polymerase to bind less efficiently. There are also mutations that might increase the binding affinity of RNA polymerase for the promoter. Depending on the exact location and nature of the mutation, it could either increase or decrease the rate of transcription.

Connecting Altered Transcription and Gene Expression

Because gene expression is ultimately a process to produce proteins, the rate of transcription directly affects protein production. If transcription levels are too low, it might result in a deficit of the required protein, leading to possible dysfunction or disease. On the other hand, if transcription levels are too high, then too much of a protein could be produced, which might lead to a different kind of dysfunction or disease.

Examples of Diseases Related to Promoter Mutation

Promoter mutations are known to cause a variety of diseases. For example, mutations in the promoter region of the TERT gene, a critical component of the enzyme telomerase, have been associated with several types of cancer.