Final answer:
Mutations in the promoter region can alter the transcription of a gene by changing the DNA sequence where transcription factors bind, which can either decrease or increase the rate of transcription, or completely cease it. Correct option is A.
Step-by-step explanation:
A mutation within the promoter region of a gene can significantly alter the transcription of that gene. This can occur because the promoter region contains specific DNA sequences that are crucial for the binding of transcription factors and RNA polymerase. These components are necessary to initiate the process of transcription, where DNA is transcribed into messenger RNA (mRNA).
When mutations such as point mutations, insertions, or deletions occur in the promoter region, they can change the sequence where transcription factors bind. This alteration can decrease the rate of transcription by making it more difficult for transcription factors to bind to the promoter. Conversely, some mutations might increase the rate of transcription by creating a binding site with higher affinity for transcription factors or by allowing transcription factors to bind more freely.
In extreme cases, mutations can completely prevent transcription factor binding, ceasing the transcription of the adjacent gene altogether. This relationship between promoter mutations and transcriptional regulation is particularly important in the context of diseases such as cancer, where altered transcription can lead to aberrant gene expression and uncontrolled cell growth.